Long, Robert W., author
W.B. Saunders, 1976
Buku Teks
Balbach, Margaret, author
Brace Jovanovich College, 1991
Buku Teks
Cooper, Melanie M., author
McGraw-Hill, 2009
Buku Teks
Gerking, Shelby D., author
Burgess, 1970
Buku Teks
Patterson, C.O. Pat, author
Burgess Publishing , 1973
Buku Teks