Cita APA (7a ed.)

Barké, C. R., & Nicholas, D. R. (1990). Physical activity in older adults: The stages of change. [s.n.].

Cita Chicago Style (17a ed.)

Barké, Charles R., y Donald R. Nicholas. Physical Activity in Older Adults: The Stages of Change. [S.l.]: [s.n.], 1990.

Cita MLA (9a ed.)

Barké, Charles R., y Donald R. Nicholas. Physical Activity in Older Adults: The Stages of Change. [s.n.], 1990.