@article{Aho:JACM:1968,
    Address = {New York, NY, USA},
    Author = {Aho, Alfred V.},
    ISSN = {0004-5411},
    Journal = {J. ACM},
    Keywords = {indexed grammars and no pdf},
    Month = {October},
    Number = {4},
    Pages = {647--671},
    Publisher = {ACM},
    Title = {Indexed Grammars - An Extension of Context-Free Grammars},
    URL = {http://doi.acm.org/10.1145/321479.321488},
    Volume = {15},
    Year = {1968},
    acmid = {321488},
    bdsk-url-1 = {http://doi.acm.org/10.1145/321479.321488},
    bdsk-url-2 = {http://dx.doi.org/10.1145/321479.321488},
    date-added = {2013-12-10 14:13:04 +0000},
    date-modified = {2016-01-16 15:21:28 +0000},
    issue_date = {Oct. 1968},
    numpages = {25},
    doi = {10.1145/321479.321488}
}

@article{Aho:JACM:1968, Address = {New York, NY, USA}, Author = {Aho, Alfred V.}, ISSN = {0004-5411}, Journal = {J. ACM}, Keywords = {indexed grammars and no pdf}, Month = {October}, Number = {4}, Pages = {647--671}, Publisher = {ACM}, Title = {Indexed Grammars - An Extension of Context-Free Grammars}, URL = {http://doi.acm.org/10.1145/321479.321488}, Volume = {15}, Year = {1968}, acmid = {321488}, bdsk-url-1 = {http://doi.acm.org/10.1145/321479.321488}, bdsk-url-2 = {http://dx.doi.org/10.1145/321479.321488}, date-added = {2013-12-10 14:13:04 +0000}, date-modified = {2016-01-16 15:21:28 +0000}, issue_date = {Oct. 1968}, numpages = {25}, doi = {10.1145/321479.321488} }