Akhtar, Shahid
International Development Research Centre, 1975
Buku Teks
Lewin, A. C.
John Wiley & Sons, 1981
Buku Teks
Artikel Jurnal
Kemp, Herman C.
KITLV Press, 1990
Buku Referensi
Groenendael, Victoria M. Clara van
Foris Publications, 1987
Buku Referensi