APA Format
Kotler, Philip
; Armstrong, Gary
. (1994, 1999). Principles of marketing. Upper Saddle River, NJ : Prentice-Hall
MLA Format
Kotler, Philip; Armstrong, Gary
. Principles of marketing. Upper Saddle River, NJ : Prentice-Hall, 1994, 1999
Australian/Harvard Format
Kotler, Philip
; Armstrong, Gary
. 1994, 1999. Principles of marketing. Prentice-Hall, Upper Saddle River, NJ
Warning: These citations may not always be 100% accurate.