Jones, Gareth R., author
Pearson Education. Inc, 2004
Buku Teks
Hatch, Mary Jo
Oxford University Press, 1997
Buku Teks
John Wiley & Sons, 1959
Buku Teks
Ross, Murray G., author
Harper & Row , 1967
Buku Teks
Jay M. Shafritz, J. Steven Ott, editor
Harcourt College, 2001
Buku Teks