求theory prob.appl里面的三篇文章 ！
Controlled semi-markov and markov jump processes average cost criterion (1985)   Kitaev,M.Yu
Markov controlled models with countable state space and continuous time  (1977)   Yushkevich,A.A
On homogeneous Markov models with continuous time and finite or countable state space   (1979)   Yushkevich,A.A
前两篇找不到网址，下面试最后一篇的网址。
http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=TPRBAU000024000001000156000001&idtype=cvips&gifs=yes