Zelinsky, Marilyn
McGraw-Hill, 1997
Buku Teks SO
Richard, Paul
Omiwa Jinsha Press, 1976
Koleksi Publik
edited by James F. Scotton and William A. Hachten
Wiley-Blackwell, 2010
eBooks
Din, Rasshied
Conran Octopus, 2000
Buku Referensi
Jakarta : The Ambassador of The Republic of Zimbabwe, 2007,
Majalah, Jurnal, Buletin