@Article{	  die86ai,
  author	= "Volker Diekert",
  journal	= "Acta Informatica",
  pages		= "679--698",
  title		= "Investigations of {H}otz groups for arbitrary grammars",
  volume	= "22",
  number	= "6",
  year		= "1986",
  doi		= "10.1007/BF00263651"
}