(1980). Petroleum committee: Nine session, Geneva, 1980: General report. Geneva, Switzerland: International Labour Office.
Dyfyniad Arddull ChicagoPetroleum Committee: Nine Session, Geneva, 1980: General Report. Geneva, Switzerland: International Labour Office, 1980.
Dyfyniad MLAPetroleum Committee: Nine Session, Geneva, 1980: General Report. Geneva, Switzerland: International Labour Office, 1980.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.