I'm considering the minimum set cover problem with the constraint that each set contains at most $k$ elements. Here, $k$ depends on the size of the universe.
For example, $k$ may equal $\log n,\sqrt n$, etc., if the universe is $\{1,2,\ldots,n\}$.
In this post and this paper of Luca Trevisan, they seem to deal with constant $k$. In this paper of Uriel Feige, there is no size bound.
Though I suspect it is still $(1-o(1))\ln k$ inapproximable, any reference on this would be nice.