APA (7th ed.) Citation

Safari Tech Books Online & Walsh, N. A. (1999). Learning Perl/TK. O'Reilly.

Chicago Style (17th ed.) Citation

Safari Tech Books Online and Nancy Author Walsh. Learning Perl/TK. [Place of publication not identified]: O'Reilly, 1999.

MLA (9th ed.) Citation

Safari Tech Books Online and Nancy Author Walsh. Learning Perl/TK. O'Reilly, 1999.