APA (7th ed.) Citation

Heckel, P. (1991). The elements of friendly software design (2nd ed.). Sybex.

Chicago Style (17th ed.) Citation

Heckel, Paul. The Elements of Friendly Software Design. 2nd ed. San Francisco, Calif. [u.a.]: Sybex, 1991.

MLA (9th ed.) Citation

Heckel, Paul. The Elements of Friendly Software Design. 2nd ed. Sybex, 1991.