Harbeck, Richard M.
Holt Rinehart and Winston, 1965
Buku Teks
Merken, Melvin
Saunders College Publishing, 1993
Buku Teks
Hewitt, Paul G.
Addison-Wesley, 2010
Buku Teks
McCarthy, Francis W.
Allyn and Bacon, 1972
Buku Teks
Strickland, Warren L.
Burgess , 1964
Buku Teks