Ulmer, Melville J.
Houghton Miffiln, 1959
Buku Teks
Colander, David C.
McGraw-Hill, 2004
Buku Teks
Carson, Richard L.
Macmillan, 1973
Buku Teks
Frain, H. LaRue
Hougton Mifflin Company, 1937
Buku Teks
Mehta, J.K.
Caitanya Publishing House, 1967
Buku Teks