@Article{	  dl02ijac,
  author	= "Volker Diekert and Markus Lohrey",
  year		= "2002",
  title		= "A note on the existential theory of equations in plain
		  groups",
  journal	= "International Journal of Algebra and Computation",
  volume	= "12",
  pages		= "1--7",
  doi		= "10.1142/S0218196702000870"
}