This is somewhat tricky articles case:
For a background on X, see ..
For background on X, see ..
By background, I mean background about a specific topic to build knowledge on it.
It sounds more complete to say:
For a background on X, see ...
The form without the indefinite article somehow sounds incomplete.
If you use the indefinite article, it is not self-understood that the background is just a slice of information. It can be many slices of information from many areas, but all these slices together do not provide 100% of the background.
If you use the definite article:
For the background on X, see ...
than the referenced "location" ("see ...") is supposed to provide all the details.