Joost-Pieter Katoen Daniel Klink Martin Leucker Verena Wolf Abstraction for Stochastic Systems by Erlang's Method of Stages. 279-294 2008 CONCUR http://dx.doi.org/10.1007/978-3-540-85361-9_24 conf/concur/2008 db/conf/concur/concur2008.html#KatoenKLW08