Lubis, Lukmanda Evan, author
2011
UI - Skripsi (Open)
Ruff, F.
Elsevier, 1994
Buku Teks
Bell, R.P.
Cornell University, 1959
Buku Teks
Dasent, W.E., author
IKIP Semarang Press, 1982
Buku Teks
edited by S. Amelinckx, R. Gevers, J. Van Landuyt
North-Holland , 1979
Buku Teks