Marcel Dhiflaoui Stefan Funke Carsten Kwappik Kurt Mehlhorn Michael Seel Elmar Schömer Ralph Schulte Dennis Weber Certifying and repairing solutions to large LPs how good are LP-solvers? 255-256 2003 conf/soda/2003 SODA http://dl.acm.org/citation.cfm?id=644108.644152 db/conf/soda/soda2003.html#DhiflaouiFKMSSSW03