Soderquist, Larry D.
Va. : Michie, c, 1991
Buku Teks
Babb, Hugh W., author
Foundation Press , 1959
Buku Teks
Cary, William L.
The Foundation Press, 1970
Buku Teks
Schlesinger, Rudolf B.
The Foundation Press, 1950
Buku Teks
Kauper, Paul G., author
Little, Brown, 1971
Buku Teks