MLA

Peeters, S, and Séra de Vriendt. Linguistics In Belgium. Brussel: Didier, 1977.

APA

Peeters, S., & de Vriendt, S. (1977). Linguistics in Belgium. Brussel: Didier.

Chicago

Peeters, S. ed., and Séra de Vriendt ed. Linguistics In Belgium. Brussel: Didier, 1977.