Changsheng Zhang Jigui Sun Xingjun Zhu Qingyun Yang An improved particle swarm optimization algorithm for flowshop scheduling problem. 204-209 2008 108 Inf. Process. Lett. 4 http://dx.doi.org/10.1016/j.ipl.2008.05.010 db/journals/ipl/ipl108.html#ZhangSZY08