Ken-ichi Kawarabayashi Atsuhiro Nakamoto Yusuke Suzuki N-flips in even triangulations on surfaces. 229-246 2009 99 J. Comb. Theory, Ser. B 1 http://dx.doi.org/10.1016/j.jctb.2008.06.006 db/journals/jct/jctb99.html#KawarabayashiNS09