Abstract
We show that the usual Hodge conjecture implies the general Hodge conjecture for certain abelian varieties of type III, and use this to deduce the general Hodge structure for all powers of certain $4$-dimensional abelian varieties of type III. We also show the existence of a Hodge structure $M$ such that $M$ occurs in the cohomology of an abelian variety, but the Tate twist $M(1)$ does not occur in the cohomology of any abelian variety, even though it is effective.
