## 21.2 Topics

Here are some topics that should be discussed in this chapter, and have not yet been written.

Cohomology of a sheaf of modules on a site is the same as the cohomology of the underlying abelian sheaf.

Hypercohomology on a site.

Ext-groups.

Ext sheaves.

Tor functors.

Higher direct images for a morphism of sites.

Derived pullback for morphisms between ringed sites.

Cup-product.

Group cohomology.

Comparison of group cohomology and cohomology on $\mathcal{T}_ G$.

Čech cohomology on sites.

Čech to cohomology spectral sequence on sites.

Leray Spectral sequence for a morphism between ringed sites.

Etc, etc, etc.

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