The title says it all. Despite heavy googling I have not been able to find anything. What I am interested in, is theory (maybe modelling), not for the moment finite difference methods as approximations to partial differential equations! Books, papers, webpages, ....



Reference/Introduction to partial   difference(NOT differential!)  equations
[Partial Difference Equations](http://books.google.com/books?id=1klnDGelHGEC) by Sui Sun Cheng? A good start (in the context of reading the classics) is the paper by [Courant-Friedrichs-Lewy](http://www.amath.washington.edu/~narc/win08/papers/courant-friedrichs-lewy.pdf). Also useful is a list with [more books](http://www.ericweisstein.com/encyclopedias/books/FiniteDifferenceEquations.html).


For the non-partial case, I must admit I have a soft spot for [Milne-Thompson](http://books.google.com/books?id=NXRLajGtgjEC&printsec=frontcover&dq=%22The+Calculus+of+Finite+Differences%22&source=bl&ots=Z84L819X7z&sig=frrl3VuChAoRCmtDZcd032TcZr0&hl=en&ei=YB0ZTI3xJImDnQfO_uC1Cg&sa=X&oi=book_result&ct=result&resnum=1&ved=0CBIQ6AEwAA#v=onepage&q&f=false)'s book.


