• with so small an effort"

  • It wouldn't be that bad a job.

  • good a person
Can someone please explain (or give me a reference explaining) such constructions: adjective + article + noun?

Thank you
I'm not sure how much there is to explain, so I'll just make some random comments.

The whole pattern includes an intensifier like so or that, and the article has to be the indefinite article (a / an).

intensifier + adjective + a/an + noun.

And the pattern is approximately equivalent to

a/an + noun + which [is / was / ...] + intensifier + adjective.

It wouldn't be that bad a job.

It wouldn't be a job which was that bad.

... with so small an effort.
... with an effort which is/was so small.

Was it that exciting a movie?
Was it a movie which was that exciting?

This is too expensive a car for us.
This is a car which is too expensive for us.

Great answer, thanks. I knew when to use it, just couldn't explain it. Cheers.