by Radiks Purba $13.00
by K. Bertens $7.00
by Prof. Ir. Amris Makmur $6.00
by Victor Lazarro $12.00
by Prof. DR. Taliziduhu Ndraha $11.00
by Prof. DR. H. Abdul Muis Ba'dulu & Hermann, S.Ag., M.Pd $7.00