@article{Sagiv:1980:ERE:322217.322221,
    Address = {New York, NY, USA},
    Author = {Sagiv, Yehoshua and Yannakakis, Mihalis},
    File = {Equivalences Among Relational Expressions with the Union and Difference Operators - Sagiv, Yannakakis (0) (0) - a - a - x.pdf},
    ISSN = {0004-5411},
    Journal = {J. ACM},
    Month = {October},
    Number = {4},
    Pages = {633--655},
    Publisher = {ACM},
    Title = {Equivalences Among Relational Expressions with the Union and Difference Operators},
    URL = {http://doi.acm.org/10.1145/322217.322221},
    Volume = {27},
    Year = {1980},
    acmid = {322221},
    bdsk-url-1 = {http://doi.acm.org/10.1145/322217.322221},
    bdsk-url-2 = {http://dx.doi.org/10.1145/322217.322221},
    date-added = {2014-07-29 07:52:39 +0000},
    date-modified = {2014-07-29 07:52:39 +0000},
    issue_date = {Oct. 1980},
    numpages = {23},
    doi = {10.1145/322217.322221}
}

@article{Sagiv:1980:ERE:322217.322221, Address = {New York, NY, USA}, Author = {Sagiv, Yehoshua and Yannakakis, Mihalis}, File = {Equivalences Among Relational Expressions with the Union and Difference Operators - Sagiv, Yannakakis (0) (0) - a - a - x.pdf}, ISSN = {0004-5411}, Journal = {J. ACM}, Month = {October}, Number = {4}, Pages = {633--655}, Publisher = {ACM}, Title = {Equivalences Among Relational Expressions with the Union and Difference Operators}, URL = {http://doi.acm.org/10.1145/322217.322221}, Volume = {27}, Year = {1980}, acmid = {322221}, bdsk-url-1 = {http://doi.acm.org/10.1145/322217.322221}, bdsk-url-2 = {http://dx.doi.org/10.1145/322217.322221}, date-added = {2014-07-29 07:52:39 +0000}, date-modified = {2014-07-29 07:52:39 +0000}, issue_date = {Oct. 1980}, numpages = {23}, doi = {10.1145/322217.322221} }