Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Networks of Queues Models with Several Classes of Customers and
  Exponential Service Times   The main target of this paper is to present the Markov chain C that, not
giving explicitly the queue lengths stationary probabilities, has the necessary
information to its determination for open networks of queues with several
classes of customers and exponential service times, allowing to overcome
ingeniously this problem. The situation for closed networks, in the same
conditions, much easier is also presented.

1
The categories of this paper are: cs
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
22
The categories of this paper are: chao-dyn
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
6
The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
4
The categories of this paper are: cond-mat
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
19
The categories of this paper are: eess