by Dr. Sofyan Syafri Harahap, M.S,Ac $12.00
by Prof. Dr. Suharsimi Arikunto $11.00
by Drs. Basir Barthos $11.00
by Mansur Samin $6.00
by A. Tresna Sastrawijaya, M.Sc $7.00
by Hawari, Dadang $6.00