expand on something
expand upon something

However, he does not expand upon the theory later in the film.

The story expanded further upon that of the original game.

We need to take into account a common man's view and expand upon it.

The group continue to expand upon the experimental nature of their music.

I am hoping to take their work and expand upon it.

It is hoped to expand upon these activities in the future.

These problems are not expanded upon or resolved during the show's run.

The distinction between the two most common systems is expanded upon in the next section.

But would they I wonder, if it was expanded upon slightly?

The character has since been expanded upon by other designers.