Clark D. Moore and Ann Dunbar
Praeger Publishers, 1968
Buku Teks
Sage Publications, 1980
Buku Teks
Ahuja, B. N.
Surjeet Publications, 1989
Buku Teks
Berita Publishing Sdn Bhd, 1993
Buku Referensi
edited by C. Grove Haines
John Hopkins Press, 1956
Buku Teks