Special publication. (1980). Proceedings of symposium on drilling technology and engineering aids to geoogical exploration calcutta 12th to 15th february 1980: Special publication No.4. Geological Survey of India.
Dyfyniad Arddull ChicagoSpecial publication. Proceedings of Symposium on Drilling Technology and Engineering Aids to Geoogical Exploration Calcutta 12th to 15th February 1980: Special Publication No.4. Newdelhi: Geological Survey of India, 1980.
Dyfyniad MLASpecial publication. Proceedings of Symposium on Drilling Technology and Engineering Aids to Geoogical Exploration Calcutta 12th to 15th February 1980: Special Publication No.4. Geological Survey of India, 1980.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.