McSwain, Norman E.
MosbyJem, 2003
Buku Teks
Du Gas, Beverly Witter
W.B. Saunders, 1983
Buku Teks
Curran, Desmond
Churchill, Livingtone, 1972
Buku Teks
Olumoroti, Olumuyiwa John
Elsevier, 2005
Buku Teks
Goldman, Howard H.
Prentice-Hall, 1995
Buku Teks