@book{143976,
	author = {Lorentzen, Rolf J. and Petrobras and SPE Annual Technical Conference and Exhibition (2001 sept. 30-3 oct. : New Orleans) and Fjelde, Kjell Kare and Petrobras},
	title = {Underbalanced and low-head drilling operations},
	note = {Disponible en formato PDF.}
}