@Article{	  adhp2005,
  author	= "Holger Austinat and Volker Diekert and Ulrich Hertrampf
		  and Holger Petersen",
  journal	= "Theoretical Computer Science",
  title		= "Regular Frequency Computations",
  volume	= "330",
  number	= "1",
  year		= "2005",
  pages		= "15--21",
  doi		= "10.1016/j.tcs.2004.09.007"
}