Doris, Lillian
Prentice-Hall, 1970
Buku Referensi
Brenner, Gary
Prentice-Hall, 1990
Buku Referensi
Jorgensen, Finn
The McGraw-Hill Companies, 1996
Buku Referensi
De Vries, Mary Ann
Prentice-Hall, 1991
Buku Referensi
edited by Robert Holman Coombs
Sage, 2001
Buku Referensi