The official military manual " Vạn Kiếp Tông Bí Truyền Thư
: Offers the Hán tự (Chinese characters) and Vietnamese translation of the preface. Thivien.net : Contains the full text of the preface. 2. PDF Compilations (Secondary Sources)
A simple Google search for "Van Kiep Tong Bi Truyen Thu PDF" often leads to dead ends. Here is the best way to access verified teachings:
Based on historical descriptions in the Đại Việt Sử Ký Toàn Thư , the book focused on: