Erika Ábrahám-Mumm Martin Steffen Ulrich Hannemann Verification of Hybrid Systems: Formalization and Proof Rules in PVS. 48-57 2001 conf/iceccs/2001 ICECCS http://csdl.computer.org/comp/proceedings/iceccs/2001/1159/00/11590048abs.htm db/conf/iceccs/iceccs2001.html#Abraham-MummSH01