@article{ruohonen83,
    Author = {Ruohonen, Keijo},
    File = {On some variants of Post's Correspondence Problem - Ruohonen (0) (0) - a - a - h.pdf},
    ISSN = {0001-5903},
    Journal = {Acta Informatica},
    Language = {English},
    Number = {4},
    Pages = {357-367},
    Publisher = {Springer-Verlag},
    Title = {On some variants of Post's Correspondence Problem},
    URL = {http://dx.doi.org/10.1007/BF00290732},
    Volume = {19},
    Year = {1983},
    bdsk-url-1 = {http://dx.doi.org/10.1007/BF00290732},
    date-added = {2013-10-05 21:21:41 +0000},
    date-modified = {2013-10-05 21:21:41 +0000},
    doi = {10.1007/BF00290732}
}

@article{ruohonen83, Author = {Ruohonen, Keijo}, File = {On some variants of Post's Correspondence Problem - Ruohonen (0) (0) - a - a - h.pdf}, ISSN = {0001-5903}, Journal = {Acta Informatica}, Language = {English}, Number = {4}, Pages = {357-367}, Publisher = {Springer-Verlag}, Title = {On some variants of Post's Correspondence Problem}, URL = {http://dx.doi.org/10.1007/BF00290732}, Volume = {19}, Year = {1983}, bdsk-url-1 = {http://dx.doi.org/10.1007/BF00290732}, date-added = {2013-10-05 21:21:41 +0000}, date-modified = {2013-10-05 21:21:41 +0000}, doi = {10.1007/BF00290732} }