@article{Rossman:JACM:2008,
    Address = {New York, NY, USA},
    Author = {Rossman, Benjamin},
    File = {Homomorphism Preservation Theorems - hpt-jacm - a - a - a - r.pdf},
    ISSN = {0004-5411},
    Journal = {J. ACM},
    Keywords = {first-order logic, preservation theorems, conjunctive queries, Finite model theory, quantifier-rank, homomorphisms, tree-depth},
    Month = {August},
    Number = {3},
    Publisher = {Association for Computing Machinery},
    Title = {Homomorphism Preservation Theorems},
    URL = {https://doi.org/10.1145/1379759.1379763},
    Volume = {55},
    Year = {2008},
    articleno = {Article 15},
    bdsk-url-1 = {https://doi.org/10.1145/1379759.1379763},
    date-added = {2020-02-13 18:01:41 +0100},
    date-modified = {2020-02-15 12:43:49 +0100},
    issue_date = {July 2008},
    numpages = {53},
    doi = {10.1145/1379759.1379763}
}

@article{Rossman:JACM:2008, Address = {New York, NY, USA}, Author = {Rossman, Benjamin}, File = {Homomorphism Preservation Theorems - hpt-jacm - a - a - a - r.pdf}, ISSN = {0004-5411}, Journal = {J. ACM}, Keywords = {first-order logic, preservation theorems, conjunctive queries, Finite model theory, quantifier-rank, homomorphisms, tree-depth}, Month = {August}, Number = {3}, Publisher = {Association for Computing Machinery}, Title = {Homomorphism Preservation Theorems}, URL = {https://doi.org/10.1145/1379759.1379763}, Volume = {55}, Year = {2008}, articleno = {Article 15}, bdsk-url-1 = {https://doi.org/10.1145/1379759.1379763}, date-added = {2020-02-13 18:01:41 +0100}, date-modified = {2020-02-15 12:43:49 +0100}, issue_date = {July 2008}, numpages = {53}, doi = {10.1145/1379759.1379763} }