Epstein, Cynthia Fuchs
University of Califoenia Press , 1970
Buku Teks
Vanvugt, Ewald, 1943-
Aspekt, 2003
Buku Teks
Barrow, John D.
Oxford University Press , 1998
Buku Teks SO
Brown, Sheldon S.
VGM Career Horizons, 1994
Buku Teks
Paradis, Adrian A.
VGM Career Books, 2001
Buku Teks