Cita APA (7a ed.)

Harley, B. (1993). The development of second language proficiency ([1st. ed., 2nd. pr.].). Cambridge University Press.

Cita Chicago Style (17a ed.)

Harley, Birgit. The Development of Second Language Proficiency. [1st. ed., 2nd. pr.]. Cambridge, United Kingdom: Cambridge University Press, 1993.

Cita MLA (9a ed.)

Harley, Birgit. The Development of Second Language Proficiency. [1st. ed., 2nd. pr.]. Cambridge University Press, 1993.