Dyfyniad APA

(1989). GSI records. Geological survey.

Dyfyniad Arddull Chicago

GSI Records. India: Geological survey, 1989.

Dyfyniad MLA

GSI Records. Geological survey, 1989.

Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.