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},
}