
See:
   Maureen Stone and Tony DeRose,
   "A Geometric Characterization of Parametric Cubic Curves",
   ACM TOG, vol 8, no 3, July 1989, pp. 147-163.
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...Ron Capelli                 IBM Corp.  Dept. C13,  MS. P230
   capelli@vnet.ibm.com        PO Box 950
   (914) 435-1673              Poughkeepsie, NY  12602
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