Artikel Jurnal
McGivney, Veronica
The National Institute of Adult Continuing Education, 1991
Buku Teks
Jossey - Bass Publishers , 1996
Buku Teks
A.G. Lunandi, author
Gramedia, 1989
Buku Teks
A.A. (Ali Akhbar) Navis, 1924-, author
Grasindo, 1996
Buku Teks