@InProceedings{	  LohSen06,
  author	= "Markus Lohrey and G{\'e}raud S{\'e}nizergues",
  title		= "Theories of {HNN}-Extensions and Amalgamated Products",
  booktitle	= "ICALP",
  year		= "2006",
  pages		= "504--515",
  crossref	= "DBLP:conf/icalp/2006-2",
  bibsource	= "DBLP, http://dblp.uni-trier.de",
  doi		= "10.1007/11787006_43"
}