@incollection{Blass_1987,
    doi = {10.1007/3-540-18170-9_151},
    url = {https://doi.org/10.1007%2F3-540-18170-9_151},
    year = {1987},
    publisher = {Springer Berlin Heidelberg},
    pages = {20--36},
    author = {Andreas Blass and Yuri Gurevich},
    title = {Existential fixed-point logic},
    booktitle = {Computation Theory and Logic}
}

@incollection{Blass_1987, doi = {10.1007/3-540-18170-9_151}, url = {https://doi.org/10.1007%2F3-540-18170-9_151}, year = {1987}, publisher = {Springer Berlin Heidelberg}, pages = {20--36}, author = {Andreas Blass and Yuri Gurevich}, title = {Existential fixed-point logic}, booktitle = {Computation Theory and Logic} }