?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.au=Jastram%2C+Michael&rft.aulast=Jastram&rft.aufirst=Michael&rft.date=2010&rft.title=An+Approach+of+Requirements+Tracing+in+Formal+Refinement+&rft.genre=proceeding