@article{Apt_1991,
    doi = {10.1007/bf03037168},
    url = {https://doi.org/10.1007%2Fbf03037168},
    year = {1991},
    month = {aug},
    publisher = {Springer Science and Business Media {LLC}},
    volume = {9},
    number = {3-4},
    pages = {335--363},
    author = {Krzysztof R. Apt and Marc Bezem},
    title = {Acyclic programs},
    journal = {New Generation Computing}
}

@article{Apt_1991, doi = {10.1007/bf03037168}, url = {https://doi.org/10.1007%2Fbf03037168}, year = {1991}, month = {aug}, publisher = {Springer Science and Business Media {LLC}}, volume = {9}, number = {3-4}, pages = {335--363}, author = {Krzysztof R. Apt and Marc Bezem}, title = {Acyclic programs}, journal = {New Generation Computing} }