James T. Kajiya.
Ray Tracing Parametric Patches.
In SIGGRAPH '82: Proceedings of the 9th annual conference on Computer graphics and interactive techniques, pp. 245--254, 1982.

Bibtex:

@InProceedings{ kajiya:1982:RTP,
  author =      "James T. Kajiya",
  title =       "Ray Tracing Parametric Patches",
  booktitle =   "SIGGRAPH '82: Proceedings of the 9th annual
                 conference on Computer graphics and interactive
                 techniques",
  pages =       "245--254",
  year =        "1982",
}