An Ngo-The Günther Ruhe Wei Shen Release Planning under Fuzzy Effort Constraints. 168-175 2004 conf/IEEEicci/2004 IEEE ICCI http://csdl.computer.org/comp/proceedings/icci/2004/2190/00/21900168abs.htm db/conf/IEEEicci/IEEEicci2004.html#Ngo-TheRS04