@ARTICLE{Tarjan72depthfirst,
    author = {Robert Tarjan},
    title = {Depth first search and linear graph algorithms},
    journal = {SIAM JOURNAL ON COMPUTING},
    year = {1972},
    volume = {1},
    number = {2}
}

@MISC{Palmgren_SemHeyting,
    author = {Erik Palmgren},
    title = {Semantics of intuitionistic propositional logic},
    year = {2009},
    publisher = {Uppsala University},
    howpublished = {Notes de cours}
}