@Article{	  HolubN07acm,
  author	= "Holub, {\v{S}}t\v{e}p{\'a}n and Nowotka, Dirk",
  title		= "Periodicity and Unbordered Words: A Proof of the Extended
		  Duval Conjecture",
  year		= "2007",
  journal	= "Journal of the ACM",
  volume	= "54",
  publisher	= "ACM",
  note		= "Conference version: STACS 2004",
  doi		= "10.1145/1255443.1255448"
}