Humphrey, Don D., author
Frederick A. Praeger , 1962
Buku Teks
O`Day, Rosemary
London Macmillan 1994,
Buku Teks
Gustavo De Santis, editor
Springer, 2012
eBooks
Spillebeen, Willy
Manteau , 1992
Buku Teks
Beard, Charles A., author
Free Press, 1986
Buku Teks