Landis, Paul H.
Ginn and Company, 1961
Buku Teks
Persell, Caroline Hodges, author
Harper & Row, 1984
Buku Teks
MacQueen, Donald R.
Addison-Wesley, 1973
Buku Teks
Brym, Robert J., author
Wadsworth and Cengage Learning, 2013
Buku Teks
Ross, H. Laurence (Hugh Laurence), author
McGraw-Hill, 1973
Buku Teks