Williams, Carolyn L.
American Psychological Association , 2011
Buku Teks
Wallis, W.D.
Springer, 2012
eBooks
Stapleton, Gerald F.
Tab Books, 1971
Buku Referensi
Parr, E.A.
Newness Technical Books, 1982
Buku Teks
Ward, Brice
Blue Ridge Summit TAB Books , 1971
Buku Teks