@book{153646,
	author = {National Propane Gas Association},
	title = {Propane the exceptional energy},
	publisher = {National Propane Gas Association},
	year = {2001},
	address = {Washington},
	note = {Página web visitada en enero de 2004. ; Adobe Acrobat (PDF) ; Navegadores de Internet},
	url = {http://www.npga.org/files/public/National_Energy_Policy.pdf}
}