Yogesh Singh Anju Saha Enhancing Data Flow Testing of Classes through Design by Contract. 567-574 2008 ACIS-ICIS http://doi.ieeecomputersociety.org/10.1109/ICIS.2008.70 conf/ACISicis/2008 db/conf/ACISicis/ACISicis2008.html#SinghS08