@inproceedings{
    kmtapsoft,
    author = {Kilpel{\"a}inen, P. and Mannila, Heikki},
    pages = "202-214",
    booktitle = "TAPSOFT '91",
    year = "1991",
    editors = "S.\ Abramsky and T.S.E.\ Maibaum",
    title = "The tree inclusion problem"
}