David Kaufman Hyun-soo Ahn Mark Lewis On the Introduction of an Agile, Temporary Workforce into a Tandem Queueing System. 135-171 2005 51 Queueing Syst. 1-2 http://dx.doi.org/10.1007/s11134-005-2441-x db/journals/questa/questa51.html#KaufmanAL05