Berbagai pendekatan dalam proses belajar dan mengajar - S. Nasution (Bumi Aksara, 1992)
oen, c.1-4,ws.c.5/oen, c.6/ir,c.7,ws.c.8/ast c.9/ir,c.10/ast c.11-12/en, c.13/en, c.14/ws.c.16-18