Paper to read: Product-Form Stationary Distributions for Deficiency Zero Chemical Reaction Networks. David F. Anderson, Gheorghe Craciun, and Thomas G. Kurtz. Bulletin of Mathematical Biology (2010) 72: 1947–1970. 

Link, https://www.dropbox.com/s/iu2mb20u8zaqcc8/Anderson.Craciun.Kurtz_2010_BullMathBiol.pdf?dl=0