Murdock, George Peter
Africa
McGraw-Hill, 1959
 Buku Teks
Murdock, George Peter
Africa
McGraw-Hill, 1959
 Buku Teks
Nielsen, Waldemar A.
Africa
Atheneum, 1966
 Buku Teks
Africa
edited by Phillis M. Martin and Patrick O'Meara
Indiana University Press, 1995
 Buku Teks
Compton, Charles
Inside chemistry
McGarw-Hill, 1979
 Buku Teks