Cita APA (7a ed.)

Costales, B., & Allman, E. (1997). Sendmail (2nd ed.). O'Reilly.

Cita Chicago Style (17a ed.)

Costales, Bryan, y Eric Allman. Sendmail. 2nd ed. Cambridge [etc.]: O'Reilly, 1997.

Cita MLA (9a ed.)

Costales, Bryan, y Eric Allman. Sendmail. 2nd ed. O'Reilly, 1997.