@article{Birget_1992,
    title = {Intersection and union of regular languages and state complexity},
    volume = {43},
    ISSN = {0020-0190},
    url = {http://dx.doi.org/10.1016/0020-0190(92)90198-5},
    DOI = {10.1016/0020-0190(92)90198-5},
    number = {4},
    journal = {Information Processing Letters},
    publisher = {Elsevier BV},
    author = {Birget, Jean-Camille},
    year = {1992},
    month = {sep},
    pages = {185–190}
}

@article{Birget_1992, title = {Intersection and union of regular languages and state complexity}, volume = {43}, ISSN = {0020-0190}, url = {http://dx.doi.org/10.1016/0020-0190(92)90198-5}, DOI = {10.1016/0020-0190(92)90198-5}, number = {4}, journal = {Information Processing Letters}, publisher = {Elsevier BV}, author = {Birget, Jean-Camille}, year = {1992}, month = {sep}, pages = {185–190} }