@article{Flum_2001,
    doi = {10.1137/s0097539799360768},
    url = {https://doi.org/10.1137%2Fs0097539799360768},
    year = {2001},
    month = {jan},
    publisher = {Society for Industrial {\&} Applied Mathematics ({SIAM})},
    volume = {31},
    number = {1},
    pages = {113--145},
    author = {Jörg Flum and Martin Grohe},
    title = {Fixed-Parameter Tractability, Definability, and Model-Checking},
    journal = {{SIAM} Journal on Computing}
}

@article{Flum_2001, doi = {10.1137/s0097539799360768}, url = {https://doi.org/10.1137%2Fs0097539799360768}, year = {2001}, month = {jan}, publisher = {Society for Industrial {\&} Applied Mathematics ({SIAM})}, volume = {31}, number = {1}, pages = {113--145}, author = {Jörg Flum and Martin Grohe}, title = {Fixed-Parameter Tractability, Definability, and Model-Checking}, journal = {{SIAM} Journal on Computing} }