Kouji Aoyama Takanori Ugai Shigeru Yamada Akihiko Obata Extraction of Viewpoints for Eliciting Customer's Requirements based on Analysis of Specification Change Records. 33-40 2007 conf/apsec/2007 APSEC http://doi.ieeecomputersociety.org/10.1109/APSEC.2007.54 db/conf/apsec/apsec2007.html#AoyamaUYO07