@article{Carlstr_m_2008,
    doi = {10.1002/malq.200710023},
    url = {https://doi.org/10.1002%2Fmalq.200710023},
    year = {2008},
    month = {jan},
    publisher = {Wiley},
    volume = {54},
    number = {1},
    pages = {27--34},
    author = {Jesper Carlström},
    title = {A constructive version of Birkhoff{\textquotesingle}s theorem},
    journal = {Mathematical Logic Quarterly}
}

@article{Carlstr_m_2008, doi = {10.1002/malq.200710023}, url = {https://doi.org/10.1002%2Fmalq.200710023}, year = {2008}, month = {jan}, publisher = {Wiley}, volume = {54}, number = {1}, pages = {27--34}, author = {Jesper Carlström}, title = {A constructive version of Birkhoff{\textquotesingle}s theorem}, journal = {Mathematical Logic Quarterly} }