I was looking for the uses of Rouché's theorem, and I came across queuing theory. An article stated that it is a workhorse theorem in this field, but as much as I tried to find some examples on the ways it can be used I still could not.
Could someone show some examples or recommend me some articles / webpages where I can see how this theorem is used for calculating the probability generating function? (A not too complicated example would be nice.)