Modifying the source slightly is is often the shortest path to a good line breaking, even on a Bibliography and entries like
one can abbreviate the Series, shorthen the publisher to "Springer" and get a good enough output.
Sometimes that becomes almost impossible, like in the example below
where every value is fixed and cannot be shortened or enlarged in any way.
Introducing an "artificial" linebreaking in the middle of the MR number is not an option because the argument is used to build a link to the review. I frequently use
\sloppy before the references, if that does not break anything else, but here I am looking for something that could be done to the entry.
What would you do to get a good linebreak here?