@article{ogden:68,
    Author = {Ogden, William},
    ISSN = {0025-5661},
    Journal = {Mathematical systems theory},
    Keywords = {context-free languages and classic},
    Language = {English},
    Number = {3},
    Pages = {191-194},
    Publisher = {Springer-Verlag},
    Title = {A helpful result for proving inherent ambiguity},
    URL = {http://dx.doi.org/10.1007/BF01694004},
    Volume = {2},
    Year = {1968},
    bdsk-url-1 = {http://dx.doi.org/10.1007/BF01694004},
    date-added = {2013-12-23 09:37:57 +0000},
    date-modified = {2013-12-23 09:38:18 +0000},
    doi = {10.1007/BF01694004}
}

@article{ogden:68, Author = {Ogden, William}, ISSN = {0025-5661}, Journal = {Mathematical systems theory}, Keywords = {context-free languages and classic}, Language = {English}, Number = {3}, Pages = {191-194}, Publisher = {Springer-Verlag}, Title = {A helpful result for proving inherent ambiguity}, URL = {http://dx.doi.org/10.1007/BF01694004}, Volume = {2}, Year = {1968}, bdsk-url-1 = {http://dx.doi.org/10.1007/BF01694004}, date-added = {2013-12-23 09:37:57 +0000}, date-modified = {2013-12-23 09:38:18 +0000}, doi = {10.1007/BF01694004} }