Text for stochastic processes

Question

I’ve been reading a paper where they derive a Fokker Planck equation starting with some transition equations (the underlying system is a system of chemical equations). In the process, they state some results which they call standard, and cite Gardiner’s book on stochastic methods as a reference. I am not, however, very comfortable with the book, especially because it’s a handbook and not a textbook. If someone could point me to some resources which would be helpful, that’d be great. Thanks a lot!