@InProceedings{	  die91,
  author	= "Volker Diekert",
  title		= "On the concatenation of infinite traces",
  booktitle	= "Proc. 8th Annual Symposium on Theoretical Aspects of
		  Computer Science (STACS'91), Hamburg (Germany), 1991",
  editor	= "C. Choffrut and others",
  publisher	= "Springer-Verlag",
  address	= "Heidelberg",
  series	= "Lecture Notes in Computer Science",
  volume	= "480",
  year		= "1991",
  pages		= "105--117",
  note		= "Appeared also in Theoretical Computer Science
		  \cite{die93concat}",
  doi		= "10.1007/BFb0020791"
}