Are there some good books on Green function (or approximation Green function) and its application(mainly used in PDEs)? Any reply will be appreciated!



Good books on Green function?
For wave equations, a classic book by Gerard Friedlander is ``The wave equation on
curved spacetime'', which describes the Hadamard parametrix method.
There is another nice recent book by Christian Baer called Linear wave equations
on Lorentzian manifolds. 


