Hiroyuki Ozaki Katsuhiko Gondow Takuya Katayama Class Refinement for Software Evolution. 51-56 2003 conf/iwpse/2003 IWPSE http://csdl.computer.org/comp/proceedings/iwpse/2003/1903/00/19030051abs.htm db/conf/iwpse/iwpse2003.html#OzakiGK03