edited by David W. Orr
University of North Carolina Press, 1979
Buku Teks
Masson, VeNeta
Springer Publ ., 1981
Buku Teks
Berstein, Jeremy
Basic Books, 1982
Buku Teks
Olson, William Clinton
Prentice Hall International, 1994
Buku Teks
edited by Howard Newby
John Wiley & Sons, 1978
Buku Teks