Bishop, Mark (1989). Okinawan Karate. pp. 153–166. ISBN0-7136-5666-2. Chapter 9 covers Motobu-ryu and Bugeikan, two 'ti' styles with grappling and vital point striking techniques. Page 165, Seitoku Higa: "Use pressure on vital points, wrist locks, grappling, strikes and kicks in a gentle manner to neutralize an attack."