
## 21.2 Topics

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

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

2. Hypercohomology on a site.

3. Ext-groups.

4. Ext sheaves.

5. Tor functors.

6. Higher direct images for a morphism of sites.

7. Derived pullback for morphisms between ringed sites.

8. Cup-product.

9. Group cohomology.

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

11. Čech cohomology on sites.

12. Čech to cohomology spectral sequence on sites.

13. Leray Spectral sequence for a morphism between ringed sites.

14. Etc, etc, etc.

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