@article{Otto_2004,
    doi = {10.1016/j.apal.2004.04.003},
    url = {https://doi.org/10.1016%2Fj.apal.2004.04.003},
    year = {2004},
    month = {dec},
    publisher = {Elsevier {BV}},
    volume = {130},
    number = {1-3},
    pages = {173--205},
    author = {Martin Otto},
    title = {Modal and guarded characterisation theorems over finite transition systems},
    journal = {Annals of Pure and Applied Logic}
}

@article{Otto_2004, doi = {10.1016/j.apal.2004.04.003}, url = {https://doi.org/10.1016%2Fj.apal.2004.04.003}, year = {2004}, month = {dec}, publisher = {Elsevier {BV}}, volume = {130}, number = {1-3}, pages = {173--205}, author = {Martin Otto}, title = {Modal and guarded characterisation theorems over finite transition systems}, journal = {Annals of Pure and Applied Logic} }