Aroru, BD
Asian Educational service, 0
Buku Teks
penyunting, Poltak Partogi Nainggolan
Balai Pustaka, 2016
Buku Teks
Minstry Foreign Affairs, [date of publication not identified]
Buku Teks
by J. Swiericzuk ... [and others]
Pitman, 1980
Buku Teks
Fernandez, Alejandro M., author
NSDB-UP Integrated Research Program, 1977
Buku Teks