APA Style

Dahlan, M, S. (2017). Menelaah Validitas Penelitian Observasional (Cet. 1). : Sagung Seto.

MLA Style

Dahlan, Muhamad, Sopiyudin. "Menelaah Validitas Penelitian Observasional". Cet. 1 : Sagung Seto, 2017. Text.