Gupita, Rajat, foreword
Harvard Business School, 1996
Buku Referensi
Ewing, David W., author
Free Press of Glencoe, 1964
Buku Teks
Murphy, Mary E., author
Van Nostrand Reinhold, 1963
Buku Teks
Moore, Carl L., author
South-Western Publishing, 1972
Buku Teks
Pugh, D.S.
Penguin Books, 1971
Buku Teks