Olivier Bournez Oded Maler Amir Pnueli Orthogonal Polyhedra: Representation and Computation. 46-60 1999 conf/hybrid/1999 HSCC db/conf/hybrid/hscc99.html#BournezMP99 http://link.springer.de/link/service/series/0558/bibs/1569/15690046.htm