@article {Lassen:January 2004:1571-0661:1,
	author = "Lassen S.B.",
	title = "Bisimulation in Untyped Lambda Calculus - Bohm Trees and Bisimulation up to Context",
	journal = "Electronic Notes in Theoretical Computer Science",
	volume = "20",
	year = "January 2004",
	abstract = "",
	pages = "1-29(29)",
	url = "http://www.ingentaconnect.com/content/els/15710661/2004/00000020/00000001/art00083"
}