Unesco, 1978
Buku Teks
Clement, I., author
Elsevier, 2015
Buku Teks
Goetsch, David L., author
Pearson-Prentice Hall, 2004
Buku Teks
Intner, Sheila S., author
Libraries Unlimited, 1993
Buku Teks
Colombo Plan Staff College for Technician education , 1986
Buku Teks