Daniel Keren David B. Cooper Jayashree Subrahmonia Describing Complicated Objects by Implicit Polynomials. 38-53 1994 16 IEEE Trans. Pattern Anal. Mach. Intell. 1 http://doi.ieeecomputersociety.org/10.1109/34.273718 db/journals/pami/pami16.html#KerenCS94