Which preposition to use with assertive

of Occurrences 3%

A book so abstract, so assertive of theory, and standing so far apart from the world's actual course, would hardly find an audience now.

than Occurrences 2%

The horsefly is larger and more poignantly assertive than the insect which we know by that name.

about Occurrences 1%

Nothing assertive about him; not enough go, perhaps.

as Occurrences 1%

On the other hand, the "down stream" fisherman is equally assertive as to the value of his method.

Which preposition to use with  assertive