by Prof. Dr. Sondang P. Siagian, M.P.A $7.00
by $18.00
by Ir. Kaslan A. Tohir $12.00
by Drs. Johansyah Lubis, M.Pd $7.00
by $6.00
by Husein Umar $9.00
by Suharso, A.S.P $6.00