Moore, Wilbert E. (Wilbert Ellis), author
Cornell University Press , 1951
Buku Teks
Baer, Werner, author
Richard D. Irwin, 1965
Buku Teks
Lewis, William Arthur, author
University of Ghana by the Ghana Pub, 1971
Buku Teks
edited by Egbert De Vries, Jose Medina Echavarria
UNESCO, 1967
Buku Teks
Echavarria, Jose Medina, author
New York, N.Y., Unesco
Buku Teks