Heap D.A., Brian
Careers Consultants, 1986
Buku Teks
Sinaga, Martha, author
Gramedia, 2006
Buku Teks
edited by Ivor F. Goodson
Routledge, 1992
Buku Teks
Henry, Nelson B.
University of Chicago, 1957
Buku Teks
Hall, Gene Erwin 1941-, author
Sage , 2014
Buku Teks