Lane A. Hemaspaandra Christopher M. Homan Sven Kosub Klaus W. Wagner The Complexity of Computing the Size of an Interval. 1264-1300 2007 36 SIAM J. Comput. 5 http://dx.doi.org/10.1137/S0097539705447013 db/journals/siamcomp/siamcomp36.html#HemaspaandraHKW07