@Article{	  DiekertOndruschLohrey08,
  author	= "Volker Diekert and Nicole Ondrusch and Markus Lohrey",
  title		= "Algorithmic Problems on Inverse Monoids over Virtually
		  Free Groups",
  journal	= "International Journal of Algebra and Computation",
  volume	= "18",
  number	= "1",
  year		= "2008",
  pages		= "181--208",
  doi		= "10.1142/S0218196708004366"
}