Jacques D. Fleuriot Lawrence C. Paulson A Combination of Nonstandard Analysis and Geometry Theorem Proving, with Application to Newton's Principia. 3-16 1998 conf/cade/1998 CADE db/conf/cade/cade98.html#FleuriotP98 http://link.springer.de/link/service/series/0558/bibs/1421/14210003.htm