Hughes, Rebecca, author
Pearson Education, 2002
Buku Teks
Falmer Press, 1999
Buku Teks
Wilson, John A. R., author
McGraw-Hill, 1974
Buku Teks
National Training Laboratories Institute for Applied Behavioral Science
Institute for Applied Behavioral Science, 1968
Buku Teks
Donald Freeman and Jack C. Richardsand , author
Cambridge Cambridge University Press 1996
Buku Teks