edited by I. Arjang Assad, Edward A. Wasil, Gary L. Lilien
Prentice-Hall, 1992
Buku Referensi
Porter, Lyman W.
McGraw-Hill Kogakusha, 1975
Buku Teks
Steers, Richard M.
Kent Publishing, 1985
Buku Teks
Lawrence, Paul R.
Addison-Wesley, 1969
Buku Teks
Edited by Arthur C. Beck, Jr., Ellis D. Hillmar
Reading, Massachusetts Addicon-Wesley Publishing , 1972
Buku Teks