@article{Kozen_1997,
    doi = {10.1145/256167.256195},
    url = {https://doi.org/10.1145%2F256167.256195},
    year = {1997},
    month = {may},
    publisher = {Association for Computing Machinery ({ACM})},
    volume = {19},
    number = {3},
    pages = {427--443},
    author = {Dexter Kozen},
    title = {Kleene algebra with tests},
    journal = {{ACM} Transactions on Programming Languages and Systems}
}

@article{Kozen_1997, doi = {10.1145/256167.256195}, url = {https://doi.org/10.1145%2F256167.256195}, year = {1997}, month = {may}, publisher = {Association for Computing Machinery ({ACM})}, volume = {19}, number = {3}, pages = {427--443}, author = {Dexter Kozen}, title = {Kleene algebra with tests}, journal = {{ACM} Transactions on Programming Languages and Systems} }