Jeffrey M. Voas 94-95 1999 conf/compsac/1999 COMPSAC https://doi.org/10.1109/CMPSAC.1999.812682 https://doi.ieeecomputersociety.org/10.1109/CMPSAC.1999.812682 db/conf/compsac/compsac1999.html#Voas99