Arthur W. Berger Lev M. Bregman Yaakov Kogan Bottleneck analysis in multiclass closed queueing networks and its application. 217-237 1999 31 Queueing Syst. 3-4 http://dx.doi.org/10.1023/A:1019110314687 db/journals/questa/questa31.html#BergerBK99