Farbey, A.D.
Crest Publishing House, 2001
Buku Teks SO
Morse, Stephen A.
Crest Publishing House, 2001
Buku Teks SO
Surmanek, Jim
NTC Business Books, 1989
Buku Teks SO
edited by Edward C. Bursk and Dan H. Fenn
McGraw-Hill , 1956
Buku Teks
Halford, D.R.C.
Pan Books, 1971
Buku Teks