Xiaofang Zhang Changhai Nie Baowen Xu Bo Qu Test Case Prioritization Based on Varying Testing Requirement Priorities and Test Case Costs. 15-24 2007 QSIC http://doi.ieeecomputersociety.org/10.1109/QSIC.2007.57 conf/qsic/2007 db/conf/qsic/qsic2007.html#ZhangNXQ07