@Article{	  dm89rairo,
  author	= "Volker Diekert and Axel M{\"o}bus",
  journal	= "R.A.I.R.O. --- Informatique {T}h{\'e}orique et
		  Applications",
  pages		= "29--43",
  title		= "Hotz-isomorphism theorems in {F}ormal {L}anguage {T}heory",
  volume	= "23",
  year		= "1989",
  note		= "Special issue STACS~88"
}