Toshihiko Tsumaki Yoshitomi Morisawa A framework of requirements tracing using UML. 206-213 2000 conf/apsec/2000 APSEC http://csdl.computer.org/comp/proceedings/apsec/2000/0915/00/09150206abs.htm db/conf/apsec/apsec2000.html#TsumakiM00