@incollection{jantzen:87,
    Author = {Jantzen, Matthias},
    BookTitle = {Petri Nets: Central Models and Their Properties},
    Editor = {Brauer, W. and Reisig, W. and Rozenberg, G.},
    File = {Language theory of Petri nets - Jantzen (0) (0) - a - a - t.pdf},
    ISBN = {978-3-540-17905-4},
    Keywords = {Petri net language; firing sequence; closure properties; multicounter languages; intersection closed semi-AFL},
    Pages = {397-412},
    Publisher = {Springer Berlin Heidelberg},
    Series = {Lecture Notes in Computer Science},
    Title = {Language theory of Petri nets},
    URL = {http://dx.doi.org/10.1007/BFb0046847},
    Volume = {254},
    Year = {1987},
    bdsk-url-1 = {http://dx.doi.org/10.1007/BFb0046847},
    date-added = {2013-09-25 10:36:35 +0000},
    date-modified = {2013-09-25 10:36:35 +0000},
    doi = {10.1007/BFb0046847}
}

@incollection{jantzen:87, Author = {Jantzen, Matthias}, BookTitle = {Petri Nets: Central Models and Their Properties}, Editor = {Brauer, W. and Reisig, W. and Rozenberg, G.}, File = {Language theory of Petri nets - Jantzen (0) (0) - a - a - t.pdf}, ISBN = {978-3-540-17905-4}, Keywords = {Petri net language; firing sequence; closure properties; multicounter languages; intersection closed semi-AFL}, Pages = {397-412}, Publisher = {Springer Berlin Heidelberg}, Series = {Lecture Notes in Computer Science}, Title = {Language theory of Petri nets}, URL = {http://dx.doi.org/10.1007/BFb0046847}, Volume = {254}, Year = {1987}, bdsk-url-1 = {http://dx.doi.org/10.1007/BFb0046847}, date-added = {2013-09-25 10:36:35 +0000}, date-modified = {2013-09-25 10:36:35 +0000}, doi = {10.1007/BFb0046847} }