Gaya APA

Batubara, D. (1971). OMBILIN COAL FIELD WEST SUMATRA , INDONESIA . TECHNICAL REPORT OF INVESTIGATION AND EXPLORATION . . Bandung: Direktorat Batubara.

Gaya MLA

Batubara, Direktorat. "OMBILIN COAL FIELD WEST SUMATRA , INDONESIA . TECHNICAL REPORT OF INVESTIGATION AND EXPLORATION .". Bandung: Direktorat Batubara, 1971. Batubara.