APA (7th ed.) Citation

Mathison, S. (1988). Why Triangulate? Educational Researcher, 17(2), 13.

Chicago Style (17th ed.) Citation

Mathison, Sandra. "Why Triangulate?" Educational Researcher 17, no. 2 (1988): 13.

MLA (9th ed.) Citation

Mathison, Sandra. "Why Triangulate?" Educational Researcher, vol. 17, no. 2, 1988, p. 13.