Sun Lutang was a renowned martial arts master in the early 20th century who wrote extensively on various Chinese martial arts styles. His complete works, "A Study of Neiji Quan," includes his five books and essays.

In "The Study of Xing Yi Boxing," Sun explores the basics of Xing Yi Quan and its relationship to traditional Chinese medicine. He also shares his personal experiences with the style and provides insights into its practical applications.

In "The Study of Ba Gua Boxing," Sun delves into the principles and techniques of Ba Gua Zhang, a martial arts style known for its circular movements and unpredictable footwork. He emphasizes the importance of developing both internal and external strength in this style.

"The Study of Tai Ji Boxing" is Sun's comprehensive guide to Taijiquan, a soft style martial art known for its slow, flowing movements. He emphasizes the importance of relaxation, proper breathing, and mental focus in achieving mastery of this style.

In "The True Meaning of Martial Arts," Sun provides philosophical reflections on the nature and purpose of martial arts. He emphasizes the importance of cultivating virtue and wisdom, rather than just physical strength, in the practice of martial arts.

"The Study of Ba Gua Sword" is Sun's guide to the sword techniques of Ba Gua Zhang. He explores the unique features of the style's swordplay and provides detailed instructions on various sword techniques.

Finally, the essays in Sun's complete works offer his insights on various aspects of martial arts, including training methods, practical applications, and the relationship between martial arts and traditional Chinese culture.