APA

Ashworth J., Clark J., . (2002). Stepping Stones 1. Harlow: Longman.

Chicago

Ashworth J, Clark J, . 2002. Stepping Stones 1. Harlow: Longman.

Harvard

Ashworth J., Clark J., . (2002). Stepping Stones 1. Harlow: Longman.

MLA

Ashworth J, Clark J, . Stepping Stones 1. Harlow: Longman. 2002.