Cita APA (7th ed.)

Willis, S. L. (1990). Maintaining professional competence: Approaches to carrer enhancement, vitality, and success throughout a work life. Jossey-Bass.

Cita Chicago (17th ed.)

Willis, Sherry L. Maintaining Professional Competence: Approaches to Carrer Enhancement, Vitality, and Success Throughout a Work Life. San Francisco: Jossey-Bass, 1990.

Cita MLA (9th ed.)

Willis, Sherry L. Maintaining Professional Competence: Approaches to Carrer Enhancement, Vitality, and Success Throughout a Work Life. Jossey-Bass, 1990.