What is a good reference for **flat** morphisms of complex-analytic spaces? (The book by Grauert and Remmert doesn't treat them).


Topics I'm interested in: openness of flat maps, descent for coherent analytic sheaves.



Reference for flatness in complex-analytic geometry
A reference for the fact that flat maps are open in the complex-analytic category is Theorem 2.12, p. 180 in 


C. Bănică, O. Stănăşilă: *[Algebraic methods in the global theory of complex spaces](https://mathscinet.ams.org/mathscinet-getitem?mr=463470)*.


See also my answer to MO question [41158](https://mathoverflow.net/questions/41158/are-flat-morphisms-of-analytic-spaces-open/41163#41163).


