Gaya APA
Lehmann, F. (1959).
Report on The State Of The Coal Mine In The Mahakam Distric .
Bandung:
Pusat Sumber Daya Geologi.
Gaya MLA
Lehmann, F.
"Report on The State Of The Coal Mine In The Mahakam Distric".
Bandung:
Pusat Sumber Daya Geologi,
1959.
Batubara.