ASAIHL seminar on agribusiness : higher education contribution to development, Medan, Indonesia : proceedings
edited by T. Marzuki Jacob
Universitas Sumatera Utara, 1994
 Buku Referensi
Vockell, Edward L.
Educational research
Macmillan, 1983
 Buku Teks SO
Mouly, George J.
The science of educational research
American Book, 1963
 Buku Teks
Borg, Walter R.
Educational research: an introduction
David McKay, 1963
 Buku Teks
McAshan, H.H. [Hildreth Hoke]
Elements of educational research
McGraw-Hill, 1963
 Buku Teks SO