@article{Parikh:JACM:1966,
    Address = {New York, NY, USA},
    Author = {Parikh, Rohit J.},
    File = {On Context-Free Languages - Parikh (0) (0) - a - a - q.pdf},
    ISSN = {0004-5411},
    Journal = {J. ACM},
    Month = {October},
    Number = {4},
    Pages = {570--581},
    Publisher = {ACM},
    Title = {On Context-Free Languages},
    URL = {http://doi.acm.org/10.1145/321356.321364},
    Volume = {13},
    Year = {1966},
    acmid = {321364},
    bdsk-url-1 = {http://doi.acm.org/10.1145/321356.321364},
    bdsk-url-2 = {http://dx.doi.org/10.1145/321356.321364},
    date-added = {2014-11-03 14:49:52 +0000},
    date-modified = {2017-09-21 13:38:41 +0000},
    issue_date = {Oct. 1966},
    numpages = {12},
    doi = {10.1145/321356.321364}
}

@article{Parikh:JACM:1966, Address = {New York, NY, USA}, Author = {Parikh, Rohit J.}, File = {On Context-Free Languages - Parikh (0) (0) - a - a - q.pdf}, ISSN = {0004-5411}, Journal = {J. ACM}, Month = {October}, Number = {4}, Pages = {570--581}, Publisher = {ACM}, Title = {On Context-Free Languages}, URL = {http://doi.acm.org/10.1145/321356.321364}, Volume = {13}, Year = {1966}, acmid = {321364}, bdsk-url-1 = {http://doi.acm.org/10.1145/321356.321364}, bdsk-url-2 = {http://dx.doi.org/10.1145/321356.321364}, date-added = {2014-11-03 14:49:52 +0000}, date-modified = {2017-09-21 13:38:41 +0000}, issue_date = {Oct. 1966}, numpages = {12}, doi = {10.1145/321356.321364} }