Gaya APA
Collins, H. (1975).
The Re-Vitalized Coal Industries World Production Trends-10 .
Bandung:
Pusat Sumber Daya Geologi.
Gaya MLA
Collins, H.E..
"The Re-Vitalized Coal Industries World Production Trends-10".
Bandung:
Pusat Sumber Daya Geologi,
1975.
Batubara.