Frager, Robert, author
Quest Books, 1999
Buku Teks
Maltsev, Elizar
Moscow Foreign Languages Publishing House 1953
Buku Teks
edited by Chris Mace
Routledge, 1999
Buku Teks
by Jack Canfield ... [and others]
Health Communication, 1997
Buku Teks
Cosmas D. Gozali, author
Kompas Gramedia, 2012
Buku Referensi