How to cite a MathSciNet review

I checked with the head of copy-editing at Mathematical Reviews and the Mathematical Reviews librarian. Their joint answer is (using the paper mentioned by Carlo Beenakker):

If you want to add something to a reference list, the form would be:

Udrişte, Constantin, review of ``Optimal approximations by piecewise smooth functions and associated variational problems,'' (in Comm. Pure Appl. Math. 42 (1989), no. 5, 577–685, by David Mumford and Jayant Shah), Mathematical Reviews/MathSciNet MR0997568 https://mathscinet.ams.org/mathscinet-getitem?mr=997568.

If you want to mention something in text,

Constantin Udrişte (see his review published in Mathematical Reviews/MathSciNet [MR0997568]) related the Mumford-Shah results to Griffiths' law of cracks in solid mechanics.

I hope this helps.

Mathematical Reviews can be cited like any other journal, with a review number instead of volume and page numbers:

J. Smith. Review of the article “Regular doodads are widgits” by J. Doe. Mathematical Reviews 123456 (2009).

@article {review,
    AUTHOR = {Smith, J.},
    TITLE = {Review of the article ``{R}egular doodads are widgits'' by {J}. {D}oe},
    JOURNAL = {Mathematical Reviews},
    VOLUME = {123456},
    YEAR = {2009},
    ISSN = {0025-5629},
    URL = {https://mathscinet.ams.org/mathscinet-getitem?mr=123456},
}