Asymptotic Expansions for Stationary Distributions of Nonlinearly   Perturbed Semi-Markov Processes. II
  Asymptotic expansions with explicit upper bounds for remainders are given for stationary distributions of nonlinearly perturbed semi-Markov processes with finite phase spaces. The corresponding algorithms are based on a special technique of sequential phase space reduction, which can be applied to processes with an arbitrary asymptotic communicative structure of phase spaces. 
Dmitrii Silvestrov, Sergei Silvestrov
math.PR