Bagua Quan Xue (The Study of Bagua Quan) was written by Sun Lutang in 1917. It was the first book to offer detailed instruction not only in the boxing forms of Bagua Quan but on the underlying theory and philosophy. This book gives clear instructions not only in the basics of Bagua Quan and the important principles for beginners, but also clearly teaches and illustrates the major forms of the style including Single Palm Change, Double Palm Change, and the Eight Animal Changes (Lion, Qilin, Snake, Sparrowhawk, Dragon, Bear, Phoenix, Monkey). In addition Master Sun clearly shows how the postures of the boxing correspond to the Bagua Diagram and the theories of Bagua. In the last chapters Master Sun covers some advanced aspects of practice such as how to choose the practice location and time, as well as the advanced work of transforming the Shen.