by Howard W. Alexander... [et.al.]
W.A. Benjamin, 1968
Buku Teks
Makkink, H.J.
Nijgh and Van Ditmar, 1951
Buku Teks
Helling, Pam
[American Management Association, ], 1992
eBooks
Harder, Paul O
Allyn and Bacon , 1975
Buku Teks
Beason, Larry
Bredfors/ St. Martins, 2003
Buku Teks