ABSTRACT
In this chapter we collect some algebraic preliminaries, especially on spectral sequences and pure and mixed Hodge structures.
Let E be a vector space. An increasing filtration is an increasing sequence of subspaces
· · · ⊂WmE ⊂Wm+1E ⊂ · · · with ⋂
WmE = (0)
We will consider only finite filtrations, that is WmE = (0) and = E only for a finite number of m.