1. Galen. The exercise with the small ball. In: Galen: selected works (trans PN Singer). New York: Oxford University Press. p. 302.
2. Huard P, Wong M. The evolution of Chinese medicine. In: Chinese medicine. New York: McGraw Hill; 1968. p. 8–71.
3. Tipton CM. Historical perspective: the antiquity of exercise, exercise physiology and the exercise prescription for health. In: Simopoulos S, editor. Nutrition and fitness: cultural, genetic and metabolic aspects. World review of nutrition and dietetics, vol. 98. Basel: Karger; 2008. p. 198–245.
4. Henning SE. Academia encounters the Chinese martial arts. China Rev Int. 1999;6:319–32.
5. Xing Yi Quan Xue: the study of form-mind boxing by Sun Lu Tang. Translated by Albert Liu. Pacific Grove, CA: High View Publication; 1993.