Skidmore, Thomas E., author
Oxford University Press, 1984
Buku Teks
Joseph Maier, Richard W.Weatherhead
F. A. Praeger, 1964
Buku Teks
edited by Fredrick B. Pike
University of Notre Dame Press, 1959
Buku Teks
Pierson, William W., author
D. Van Nostrand, 1953
Buku Teks
Stuart, Graham H. (Graham Henry), 1887-, author
Appleton-Century-Crofts, 1955
Buku Teks