McGraw-Hill, 2003
Buku Referensi
edited by S. Tesfamariam and K. Goda
Woodhead, 2013
eBooks
Derucher, Kenneth N.
Prentice-Hall, 1981
Buku Teks
Millington, D., author
Ellis Horwood, 1981
Buku Teks
Hare, Van Court, author
Harcourt, Brace and World, 1967
Buku Teks