Pious, Richard M
Basic Books, 1944
Buku Teks
Mervin, David
Longman, 1990
Buku Teks
Corwin, Edward S.
New York University Press, 1956
Buku Teks
Schubert, Glendon A., Jr
University of Minnesota Press, 1956
Buku Teks
Longaker, Richard P.
Cornell University Press, 1962
Buku Teks