Bone, Hugh A., author
University of Washington Press, 1958
Buku Teks
Sorauf, Frank J.
Little, Brown & Co., 1988
Buku Teks
Greenstein, Fred I., author
Englewood Cliffs, 1970
Buku Teks
Neal, Harry Edward, author
Julian Messner, 1963
Buku Teks
Porter, Kirk H.
University of Illinois Press, 1966
Buku Teks