?url_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.au=Said%2C+Mar+Yah&rft.aulast=Said&rft.aufirst=Mar+Yah&rft.date=February+2009&rft.title=Class+and+State+Machine+Refinement+in+UML-B+&rft.genre=proceeding