grammaticality - "Work" (noun) is plural or singular?

I couldn't find an answer to this question by searching the archive. If it's duplicate please let me know, and I'll remove it.

I was wondeing if "work" (noun) is plural or singular? for example, I want to talk talk about "previous work" (meaning previous published papers):

Is it correct to say:

"I provide a high-level overview of the previous work, including 'their' limitations."

Or I should say:

"I provide a high-level overview of the previous work, including 'its' limitations."

I also appreciate any suggestion for a more elegant way of saying that there are "niche" in the previous papers, that I'm going to highlight.

Thanks for your help!