Colin Titmus, Paz Buttedahi, Diana Inonside, Paul Lengrand
Unesco, 1979
Buku Referensi
Hinzen, Heribert, author
Adult Education, 1982
Buku Teks
edited by Richard Edwards
Routledge, 1993
Buku Teks
Knowles, Malcolm S., author
Cambridge University Press, 1980
Buku Teks
Knowles, Malcolm S., author
Routledge, 2015
Buku Teks