Where can I find a copy of the Trinity Principle?

Three-in-one Buddhist book is available online. In search of some east, some cat and some treasure. You can also go to some old bookstores, where there are such ancient books. The Trinity School founded by Yang Gong is the mainstream of geomantic omen, and countless friends use the Trinity Theory to explore the Yin-Yang school. Three-in-one geomantic omen also has different branches, including three-in-one ancient method, three-in-one new method and three-in-one upper method.