Hjelmström, S., & Whyte, H. (1968). Say what you mean: Book one (1a. ed.). Longmans.

Hjelmström, Svante, and Henry Whyte. Say What You Mean: Book One. 1a. ed. Londres: Longmans, 1968.

Hjelmström, Svante, and Henry Whyte. Say What You Mean: Book One. 1a. ed. Longmans, 1968.