Persell, Caroline Hodges, author
Harper & Row, 1984
Buku Teks
Harris, Stephen R
Longman, 1996
Buku Teks
Clowers, Myles L., author
McGraw-Hill, 1977
Buku Teks
Tepperman, Lorne
MGraw-Hill, 1991
Buku Teks
Schrag, Clarence C., author
Harper & Row, 1963
Buku Teks