@Article{Jur98:IPL,
  author = 	 {Marcin Jurdzi{\'n}ski},
  title = 	 {Deciding the Winner in Parity Games Is in 
                  {UP}~$\cap$~co-{UP}},
  journal = 	 {Information Processing Letters},
  year = 	 1998,
  volume = 	 {68},
  number = 	 {3},
  month = 	 {November},
  pages = 	 {119--124}
}