Lesson 2: Yin and Yang Theory

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The Origins of Yin and Yang

Four to five thousand years ago China was an agrarian culture. Because the sun was the primary source of energy, sunlight or the lack thereof was used to measure time and grow crops.


Yin pictographChinese characters tell a story in stylized pictographic form. The character or glyph for yin, shown to the left, consists of a collection of several distinct characters or glyphs. The first is a hill, the “B” looking portion to the left. The top portion to the right of the character for hill is the character for the word today. Beneath this is the character meaning cloudy. Rough translation: If it’s cloudy when you’re observing the sky, then it is a Yin day, as you cannot see the sun, which represents yang.


Yang PictographYang (pictograph to the left), as previously stated, has a lot to do with sunlight. Note the same hill as you saw in the Yin pictograph. The top portion of the glyph to the right of the portion that means today represents the sun rising. A person standing on this “hill” looking at the sky sees sunshine when the sky is clear at sunrise. The bottom right portion of the glyph represents rays of sunlight. Sunny days are yang days.

The concept of the origin of yin and yang sprang from observing the day, the sun, and the season.

The Ten Thousand Things
This is a way to say “everything” in Chinese literature. Lao Tzu talks about these things frequently in the Tao Te Ching.
These things from ancient times arise from one:
The sky is whole and clear.
The earth is whole and firm.
The spirit is whole and strong.
The valley is whole and full.
The ten thousand things are whole and alive.
Kings and lords are whole, and the country is upright.
All these are in virtue of wholeness.
The origin of the ‘ten thousand things’ is the One. The One splits into yin and yang and from this split arises everything else. This is a common theme in origin stories. If you grew up in a Western culture you saw a version of this in the book of Genesis – in the beginning there is just God who then creates everything. In the Chinese origin story God becomes everything.


The Measurement of Yin and Yang

Yin and Yang are relative terms and can have shades of intensity. For instance, some days are more yang than others: winter sun is different and less yang than summer sun.

Origin of Yin and YangYin and Yang can be measured by volume and degree. Yin is measured by shadow and yang by sunlight. The deeper the shadow, the more Yin there is. The less shadow cast when the sun is out, the greater the Yang. So high noon, when no shadow would be cast by a pole held vertical to the ground, Yang would be considered to be full.

This was depicted in a sort of stylized shorthand in Chinese written texts as a long unbroken line called the Yang Xiao. Yin, which is shadow, was drawn as a broken line, which represents both the pole and the shadow it casts. This was called the Yin Xiao.

Yin Xiao and Yang Xiao combinations to represent time and season

The Yin Xiao and the Yang Xiao lines could be combined in a stylized way to represent different times of day, as shown in the pictograms below. Be familiar with these. Some schools test on them for their Foundations classes.

Sun is rising, yang is rising, yin is recedingThis literally represents sunrise. Yang is increasing and is shown moving up from below, much as the sun comes up from the horizon. Yin is decreasing and moving out of the picture, very much like the dark night sky gets lighter and lighter on the horizon until the light fills the sky. Figuratively this can also represent the concept of Spring when the yang is rising and getting stronger.

Noon or mid-day. Yang at it's fullest. Summer.This represents noon or the middle of the day. Yang is in its’ full glory. If you were measuring the time of day with a stick there would be no shadow and thus no yin. This also represents the Summer and the Summer solstice when yang is at its’ strongest.


Sunset. The increase of yin and decrease of yang. Fall.Here the sun is setting. Yin is getting stronger and yang is receding. Darkness is filling the sky. If this were used to represent a season it would represent Fall or Autumn when yin is overtaking yang.


Midnight. Full yin. Winter. Midnight. Yin is at it’s fullest, represented by twin yin xiao marks. As you might guess, this also represents Winter and the Winter Solstice when yin is full and yang is hard to find.



The Bagua or Trigrams

At some point these were compounded into groupings of three lines, still representing yin and yang in various configurations. Note the configurations below and how yin and yang combine to make some of the “ten thousand things.”

Qian or Heaven TrigramThis represents Qian or Heaven. Notice it’s all about the yang! Yang is firey and active, represents movement more than anything solid.



Kun or Earth trigramThis is Kun or Earth, which is all yin. Yin has the cool, moist, earthy, and solid quality.  That which is tangible and touchable is more earthy or yin in quality than it is yang.



Li or Fire trigramLi or Fire. You would think fire is all about yang, but it’s not. Fire needs fuel to burn. In this case, it needs the yin of wood as fuel to feed the yang.



Kan or Water trigramThis is the Kan or Water trigram. Water is mostly yin, but needs a touch of yang to make it liquid and moveable.



Zhan or Thunder trigramZhan or Thunder. The yin of the darkened sky with the movement of yang.



Gen or Mountain trigramThis is the Gen or Mountain trigram. This earth that has been driven upward by force or yang.



Xun or Wind trigramXun or Wind is very yang, but the yin below it makes it detectable to your senses.



Dui Marsh or LakeDui, which is Marsh or Lake.



Hexagrams and the I Ching

The I Ching, The Book of Changes is an ancient book of divination, one of the five classics from the era of Confucianism. The hexagrams found in the I Ching are various combinations of any of the two trigrams above, which gives a possible 64 hexagrams, representing yin and yang in various configurations.

Chinese philosophy embraces the idea that everything in the universe is in a state of dynamic flux. On this earth the source of change is the combination of yin and yang. To an agrarian culture that source of change would be linked to every day life, which depended largely on the sun. During the summer at the height of the sunshine, the energy is considered to be up. Winter is the time when the energy of recedes downward, when there is far less sun than there is at Summer Solstice.

Why on earth are we talking about this? 
Because you must take yin and yang and the seasons into account when you practice oriental medicine. Our personal qi is related to the sun and the balance of yin and yang within us. At any given moment we have a mixture of yin and yang in varying proportions. This will factor heavily into your treatments later on.


Yin and Yang Correspondences

The eight trigrams shown above have pairs of opposites. You do not need to know the trigrams, but you do need to know the correspondences.

Yin and Yang Correspondence

Please note that the Season and Directions are actually only for the Northern hemisphere. If you were to cross into the Southern hemisphere these would flip so that the season for yang would be Fall and/or Winter and yin would correspond to Spring and/or Summer, etc.

By the time the correspondence system in the chart above was developed the meaning and thoughts about yin and yang had changed significantly from the original agricultural meanings and now represented all that was opposite and complimentary.

Some random thoughts about these correspondences from Dr. Qianzhi Wu:

  • Depression is a Yin disease and stress tends to be worse in Yin seasons such as Fall and Winter (in the Northern hemisphere). An example of this is SAD or Seasonal Affected Disorder.
  • The front door of your house should face south, which brings in greater energy, fewer germs, less wind and cold. If it faces north the cold and yin influence drains the energy of the house and the inhabitants are more likely to suffer from depression.
  • The directional concepts in this correspondence chart come from the Yellow Emperor’s Classic. When one faces south, the east is on your left. Both of these things are associated with yang. As you face south the west is on your right, which is associated with yin.


The Concepts and Content of Yin and Yang

The Concepts of Yin and Yang
There are three critical concepts about yin and yang that you need to know. These show up on the NCCAOM boards with relative frequency in the Foundations board.

Yin and yang represent two related things or phenomenon which have opposite but complimentary qualities.

Yin and yang can also represent two related aspects of one thing.
Male and female are one example, but also note that every person, regardless of gender has both yin and yang in the same body. Yin and yang are two aspects of one thing. Another example is left and right sides of a person, top and bottom, front and back.

Yin and yang properties are relative, not absolute, and can be changed.

Under certain conditions, yin and yang can be changed or switched.

Yin and yang can be divided unlimitedly and are therefore always dynamic.

Tai Chi symbol with yin and yang and the seeds of each within.Yin and yang contain the seeds of each other, which is why each half the tai chi symbol to the right has a dot of the other’s color. Even at the height of yang, which is represented by the white part of the graphic, the seeds of yin are within it. This is what the I Ching, The Book of Changes, is all about.

Content of Yin and Yang
There are four aspects or parts to know:

The opposition of yin and yang.
Left is a copy of right. Top corresponds to bottom. In the opposition is the balance. In practice you will learn The Four Gates, which is LI 4 on both hands and LV 3 on both feet. This is an example of top and bottom, left and right. There is a concept and needling style you will learn later in advanced needling techniques called the balance method that reflects this concept as well.

When there is a severe change such as hot one day and very cold the next there can be repercussions such as illness due to the sudden imbalance of yin/yang. This leaves no time to transform naturally. The result is imbalance. The same thing can occur for people who work in air conditioned environments when they move from the cold of the indoor climate to the heat of summer outside. . . especially in Texas!

Yin and yang are interdependent.
They are opposite, but complementary. One cannot exist without the other and both are needed for wholism. They depend upon each other. Without yin there is no yang; without yang there is no yin.

Mutual consumption
Yin and yang cycle constantly, which is represented in the traditional yin and yang shape above (also called “tai chi symbol”). A continuous cycling of energy is expressed in this symbol. If you’re at the top of your career, money, respect…it won’t last. But if you’re at the bottom, that won’t last either! When yang is more, yin is less and vice versa.

Yang is at the top but is changing to yin. At Summer Solstice, yang is at it’s peak. By the next day yin is slowly increasing. These changes are gradual.

Application of Yin-Yang Theory in TCM

Yin/Yang theory and the anatomical structure of the body

Yin and yang are relative when compared to each other. Bear that in mind as you read on. Yin and Yang Theory as applied to the anatomical structure of the body in a brief nutshell looks like this:

Top of the Body  Yang. Closer to the heavens and the sun.
Bottom of the body  Yin. Closer to the earth.
Head  The polarity or highest point of Yang
Feet  The polarity or lowest point of Yin

Kidney 1Head and Foot

There are 361 acupoints in TCM. Of these, some are yin points and some are yang points. Points above the waist are more yang. The yang gets stronger as you move toward the top of the head. Du 20 is the Sea of Yang and is located at the very top of the head. This is the strongest yang point. Kidney 1 is a point on the sole of the foot just below the ball of the foot. It is the strongest yin point.

Left and Right

Left is considered to be more yang, while right is considered to be more yin. This comes from the Yellow Emperor’s Classic and has to do with standing and facing South considered in the Northern hemisphere to be the healthiest direction because you gather the most Qi from the sun this way. If you are facing south, the left hand is toward the East, where the sun rises and which is considered to therefore be yang. When you just can’t remember this, think about how women, who are more yin than yang, are always right. 🙂

Front and Back

The front or ventral aspect is more yin in nature while the back or dorsal aspect is more yang in nature. This, too, is from the agricultural tradition. If you were working in the field you are likely to be slightly bent over so that the part of your body that got the most sun and was thus the most yang was your back. The most shaded side is the front, and therefore yin.

Exterior and Interior

The exterior of any given thing is yang, as it is most likely to encounter the sun and is perceived to the outward, which is also associated with yang. The interior of any given thing is yin, as it is more hidden. The exterior of the body is therefore more yang and the interior of the body is more yin.

Hollow and Solid

That which is solid, like the earth, is yin. That which is hollow, like the atmosphere, is yang. On a physical level, the heart, liver, spleen, lung and kidney are “solid” organs and are thus yin. Hollow organs are stomach, small and large intestine, bladder and gallbladder and are yang.

The Dividing Lines for Yin and Yang

So where does yin turn into yang and yang turn back into yin on a human body? One spot is at the perineum, the lowest point on the trunk of the body. Ren 1 is located here. This is called Hui Yin or the Meeting of Yin. The Hui Yang (Meeting of Yang) is located very close to this and slightly posterior at a point called Bladder 35 which lies about 1 cm lateral to the tailbone.

The aspects of the extremities that are closest to the inside of the body when one is standing upright with the arms hanging down and the palms facing the sides of the thighs are the yin regions of the body. This includes the inside of the arms and the inside of the thighs). We refer to these as the “medial aspects” of the extremities. The “later aspects of the extremities” are yang regions. These are the outside edges of the body – the back of the hands, the outsides of the forearms and biceps, the region of the iliotibial (IT) band down the outside of the thigh, the outside of the lower leg.

Yin and Yang Theory for Channel/Meridian Distribution

There are three yin channels on the upper extremities and three on the lower extremities. There are three yang channels on the upper extremities and three on the lower extremities as well.

Know this chart:Hand Yin and Yang Channels and their general pathways

Note that:

The hand yang channels meet the foot yang channels at the face and head. These are places where the Yang converges.  The hand yin meridians meet the foot yin meridians at the chest.

There are 12 regular channels in the body. Memorize this chart too.

Flow of Qi

Yin Channel directionsThere are anatomical dividing lines separating yin and yang on the body, also. When you are standing with your arms at your sides and the palms facing your legs this is how it works:

Thumb – Yin on the hand
The anterior aspect of the thumb points forward, toward the Yin side of the body.

Little finger – Yang on the hand
The posterior aspect of the hand, the little finger, points posteriorly, which is pointing toward the back of the body. The back of the body, the side that would be facing the sun when you are working outside is the Yang side of the body.

Middle finger
The middle finger, ever popular in junior high and in traffic, is the dividing line between Yin and Yang on the upper extremities.

Great toe – Yin on the foot
This is the anterior aspect and is therefore the direction of Yin for the body. Think of it as the “thumb of the foot.” And actually, if we were four legged creatures instead of bipedal locomotives that would be about right!

Little toe – Yang on the foot
The little toe is on the lateral side of the body, which is more Yang.

Middle toe
This is the dividing line between Yin and Yang on the legs, much like the middle finger is the dividing line on the arms/hands.

Yin and Yang Theory in Physiology

Understanding yin and yang as it applies to health and disease states of the body is crucial in understanding how to treat as a TCM doctor.

From a physiological standpoint, yin is the material foundation of the human body while Yang is mental and physical activity. The two must be balanced, mind and body, for harmony to exist. By way of example, chewing and digestion are yang things. The body transforms that which you chew and digest into yin. Yin is then converted into yang when you perform activities, study, etc.

Putting it into semi-english: you eat food which would be material or yin, you chew and digest it which expends energy (yang). You store the potential energy and while stored it’s yin. But then you get up and do something – walk the dog, go study, play Frisbee golf – and you burn the stored resources in order to perform which is again yang in nature.

Yin and Yang Theory in Pathology

In a balanced and healthy body there is a balance between the amount if yin and the amount of yang, much like the balance shown in the tai chi symbol. Disease, however, is a disharmony or imbalance between yin and yang. Too much of one or too little of one will cause a state of disharmony which will express itself physically in the body as a disease or syndrome. With this in mind, let’s talk about yang and yin excesses then let’s talk about yin and yang deficiencies.


Excesses of yin and yang are pathological conditions. When either yin or yang are excessive, they are said to be absolutely too much.

Yang Excess

The Six Evils
Wind – Yang
Cold – Yin
Damp – Yin
Summer Heat – Yang
Heat or Fire – Yang
Dryness – Yin

Etiology of a Yang Excess
Etiology means that which causes the problem, so this section is all about where an excess of can come from.

Diet can cause a yang excess
Spicy foods and coffee are a dietary cause. They are both spicy and hot and when ingested will add to the heat or yang in the body. The herb red ginseng will also warm yang and make a body feel hot.

Invasion of external Yang pathogens
This is an external pathogen that invades and makes it past the body’s external defenses. There are six external pathogens listed in the Chinese classical works (see the sidebar) and three of these are yang in nature. When they invade the body they add to the native Yang and cause too much Yang in the body.You might think of this as having too much family over at Christmas, only with fewer dirty dishes. While having family over can be fun, imagine if they came over uninvited and stayed in your small apartment for long periods. You can have too much of a good thing!The Yang pathogens are: Wind, Summer Heat, and Heat/Fire.

Emotional disorders
Anger and irritability, specifically. That’s why we say those people are ‘hot under the collar!’

Mechanism of a Yang excess
The mechanism is what happens as a result of the etiology/cause. In this case the mechanism of a Yang excess is that Yang becomes absolutely too much.

Symptoms of a Yang excess (know these!)

Red face
High fever

Loud voice
Thirst with a desire for cold drinks
Dark yellow urine, possibly with a hot or burning sensation
Profuse sweating
Manic behavior
Tongue: red body with a yellow, dark yellow, or brownish coating
Pulse: fast (which is anything over 90bpm)

Treatment of a Yang excess
Sedate it! To sedate the yang means to remove, eliminate, dispel, disperse, clean, clear, and/or drain it. You will see removal of excesses expressed all of these ways in TCM literature. The gist of it is ‘get rid of it.’

How do you do this? Blood letting is the strongest and fastest sedation method. There are 10 “spreading” points on the finger tips. You don’t use them all at once. You bind the tip of the chosen finger/s, prick it quickly and squeeze out 3-5 drops of blood. It is often dark red. You can also do bleeding at certain non-finger tip areas such as the inner elbow (Lung 5), and the back of the knee (Bladder 40) as well as at the apex of the ear.

Pattern diagnosis of a Yang excess
You might see this in clinic speak written as Excessive Heat Symptoms.

 Yin Excess

Etiology of a Yin excess

Diet – Dairy, cold foods, and slippery foods like seaweeds will introduce extra cold/yin into the body. Some drugs will do this as well.

Invasion of an external Yin pathogen – Cold, damp, and dry are yin pathogens.

Emotional disorders – Specifically stress and depression will generate too much yin.

Yin becomes absolutely too much.

Symptoms of a Yin excess
The symptoms listed below cannot be relieved by warming therapy! This is a hallmark sign of excessive yin. 

Aversion to cold

Cold extremities
Tongue: body is normal, thin white coating
Pulse: superficial and tight

Treatment of a Yin excess
Sedate it! Always sedate an excess. To sedate the excess yin, use moxibustion on the top part of the body is sedation (on the lower part it is tonifying). Use it at the C6 point at the base of the skull on the “Du” points. Also at the L2 vertebra and on the navel. You can also sedate with herbs: make a soup with 3 pieces of onion, 3 pieces of dry chili, and 3 slices of fresh ginger.

Pattern diagnosis
Excessive cold symptom


When there is deficiency of Yin or Yang it is said that the opposite becomes relatively too much by comparison. It’s not a literal too much of one or the other, but looks that way when you compare the two. So a yang deficiency would be too little yang when compared to the level of yin. Yin will seems overblown because the yang is too weak to keep it balanced.

seesawThis is kind of like having two kids on either side of a seesaw. Let’s say both of these mythical kids are in 5th grade and weigh about 80 lbs. That would make it very easy to keep the seesaw balanced. However, if one 5th grader decides he is done with this seesaw business and puts his 1st grade cousin on the seesaw in the same seathe just vacated, then there’s a problem. The average 1st grader weighs somewhere in the 40 lb range which means there is now a seesaw imbalance. The remaining 5th grader will be sitting on the ground and the 1st grader will be up in the air with very little leverage for leveling the seesaw. By comparison the fifth grader (who was balanced just fine until his or her fellow fifth grader left) seems like too much weight.

Yang Deficiency

Etiology of a yang deficiency

Chronic stage of a cold injured disease.
Zhang Zhongjing defined the progression of Cold diseases. He stated that it starts as a Taiyang stage, progresses to a Yangming stage then to a Shaoyang stage. After this it progresses from Taiyin to Shaoyin to Jueyin.Of these six stages, Taiyang is the strongest in Yang. If the disease is untreated or treated improperly and progresses through the stages the Yang will wane (kind of burn itself out) until it is finally gone altogether. Disease treated improperly or not at all may not kill a person, but can become a chronic problem. When it does the Yang is pretty damaged and can no longer do it’s job because it just doesn’t have the umph. One of its’ jobs is to keep the body warm, so without enough yang the person in question will probably feel too chilly most of the time.A disease is called acute if it has been less than 3 weeks in the making. If it lingers longer than that it is then chronic. Chronic conditions are always deficient conditions.

When you see the term ‘overworking’ in relation to yang deficiency in a Chinese medical text this usually refers to too much sexual intercourse or masturbation. Isn’t that a fun thing to know? Overindulgence of a sexual nature is said to lead to impotence, premature ejaculation, and a low libido.

If yang is deficient, it fails to control or balance the yin. By comparison, yin becomes relatively too much.

Symptoms of a yang deficiency
These are also referred to as “deficient cold symptoms.” Yang (the warm/active/dry part of the body) is too weak so the yin (cold/wet/quiet aspect of the body) becomes relatively too much. Too little warm and relatively too much cold looks like the ones below. All of these can be alleviated by warming the body (with hot baths, heating pads, snuggling with the dog, etc.).

Yang is closely tied to Qi. The Yang and Qi of the body bring blood circulation and warmth. Without this there are a lot of pale and cold symptoms.

Memorize these signs and symptoms of Yang deficiency


Tonify with warming therapy (or moxa) on lower part of trunk and lower extremities. Typically, this is moxa on Ren 4, 6, 8. Use a piece of fresh ginger, poke holes in it with a needle and place it on Ren 8 (umbilicus). Burn a moxa cone or two on top of it. You could also use sea salt in the umbilicus (make a paper cone out of tissue paper to hold the salt or your patient will be mighty pissed!).

Another technique would be warm needle technique. You’ll learn more about this in Acupuncture Techniques. Keep card stock or index cards on you for this – cut a slit and place it around the base of your needle because you’re going to burn a ball of moxa on the top of the needle. The card around the base of the needle will keep the ashes from falling on your patient. (That’s lawsuit material, so you definitely need to keep that from happening.)

Pattern diagnosis
Deficient cold symptoms. That’s the clinic speak you’ll see in charts that refers to symptoms of yang deficiency.

Yin Deficiency


Chronic stage of a Warm injured disease
One example is a summer heat invasion. That can cause an awful lot of seating (called hyperhidrosis in med-speak), which can then cause dehydration. Dehydration is a deficiency of body fluids, which are yin in nature. That then becomes yin deficiency.

Remember how I said overworking + yang = all about sex? Well overworking + yin is a whole different party. Nothing to do with sex. Overworking in this case (and in just about every other when you’re not talking about yang) can mean doing too much of anything – work, study, partying. People who work the graveyard shift and who do shift work are particularly susceptible to this. Sleeping at night build up the yin while you rest. When you’re not resting at night, you’re burning that yin candle at both ends. Do that garbage enough and you will end up with a yin deficiency. That’s why it’s a really bad idea to pull an all-nighter, which I know you’re probably going to do anyway!

Over indulgence in sexual intercourse
Gah! What a bummer right? Why must this be so? Because this leads to fluid depletion and fluids are linked closely to yin. All body fluids and blood are yin in nature, so the loss of any of the body liquids can cause or add to yin deficiency. You might have noticed that a number of religions and spiritual systems tie celibacy into getting super serious about spiritual practice. Buddhist spiritual traditions say sex is tied up with ego and desire which leads to suffering. Looking closer, sex leads to fantasizing which makes centering the mind more difficult, which impairs meditation, which means you don’t life in the moment as easily. Yogic traditions have a similar take on it.In Chinese medicine and Daoist practices it’s a little bit different. Sexual energy is a form of qi and creative potential that should be preserved, used wisely. Squandering it leads to depletion of essence, a substance called jing you will meet in Lesson 5. Jing is a reproductive and nurturing energy.

Yin deficiency fails to control yang, so yang becomes relatively too much.

Look back at the seesaw diagram. When you lose too many “points” on the Yin side of the scale Yang then seems to be too much. Again, this is like running a bath for yourself and finding that perfect balance of hot and cold. If someone comes along (maybe even you) and turns off the cold water the temperature coming out of the spigot now feels too hot by comparison to your Goldilocks “just right” bath water. We refer to this as “deficient heat” which basically means “heat due to deficiency.”

Symptoms of Deficient Heat (aka Yin Deficient Heat)

Memorize the signs and symptoms of Yin deficiency


This whole section relates to yin and yang disorders which cause heat and cold symptoms. If the pattern diagnosis has no heat or cold signs, then it’s not Yin-Yang!
Excessive Yang = Excessive heat symptoms
Excessive Yin = Excessive cold symptoms
Deficient Yang = deficient COLD symptoms
Deficient Yin = deficient HEAT symptoms

The basic treatment principle is to tonify and nourish the Yin of the body, most often the Yin of the Kidney and Liver.

Kidney 1, Kidney 3, Kidney 6, Liver 3, Spleen 5, Bladder 52, and Bladder 43, are examples of some acupuncture points you might use for tonification.

Diet and Herbs
This is a stronger path than acupuncture. You might ask your patient to make bone soup which not only strengthens the body and nourishes Yin (especially during menopause), but also provides a lot of calcium.

Pattern Diagnosis
Deficient Heat Symptoms

Works Cited

Wu, Qianzhi. “Foundations of Chinese Medicine.” AOMA Graduate School of Integrative Medicine, Austin Texas. Fall 2007. Lecture Series.

Ni, Maoshing. The Yellow Emperor’s Classic of Medicine. Boston MA: Shambhala Publications, 1995. Print.

Beinfield, Harriet. Between Heaven and Earth. New York NY: Ballantine Books, 1991. Print.

Kaptchuk, Ted. The Web That Has No Weaver. New York NY: Congdon & Weed, 1983. Print.