Leo Dorst Rein van den Boomgaard The Support Cone: A Representational Tool for the Analysis of Boundaries and Their Interactions. 174-178 2000 22 IEEE Trans. Pattern Anal. Mach. Intell. 2 http://www.computer.org/tpami/tp2000/i0174abs.htm db/journals/pami/pami22.html#DorstB00