Cezary Kaliszyk Freek Wiedijk Certified Computer Algebra on Top of an Interactive Theorem Prover. 94-105 2007 conf/mkm/2007 Calculemus/MKM http://dx.doi.org/10.1007/978-3-540-73086-6_8 db/conf/mkm/mkm2007.html#KaliszykW07