How to cite a MathSciNet review I want to cite a MathSciNet review. Is there a standard format for that? (I couldn't find anything)
 A: 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.  
A: 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},
}

A: too long for a comment; here is a BibTeX template:
@article {MR997568,
    AUTHOR = {Mumford, David and Shah, Jayant},
    TITLE = {Optimal approximations by piecewise smooth functions and
              associated variational problems},
    JOURNAL = {Comm. Pure Appl. Math.},
    FJOURNAL = {Communications on Pure and Applied Mathematics},
    VOLUME = {42},
    YEAR = {1989},
    NUMBER = {5},
    PAGES = {577--685},
    ISSN = {0010-3640},
    CODEN = {CPAMA},
    MRCLASS = {49F20 (41A30 92A27)},
    MRNUMBER = {997568 (90g:49033)}, 
    MRREVIEWER = {Constantin Udri{\c{s}}te},
    DOI = {10.1002/cpa.3160420503},
    URL = {http://dx.doi.org/10.1002/cpa.3160420503},
}

