@article{Birkhoff_1937,
    doi = {10.1215/s0012-7094-37-00334-x},
    url = {https://doi.org/10.1215%2Fs0012-7094-37-00334-x},
    year = {1937},
    month = {sep},
    publisher = {Duke University Press},
    volume = {3},
    number = {3},
    author = {Garrett Birkhoff},
    title = {Rings of sets},
    journal = {Duke Mathematical Journal}
}

@article{Birkhoff_1937, doi = {10.1215/s0012-7094-37-00334-x}, url = {https://doi.org/10.1215%2Fs0012-7094-37-00334-x}, year = {1937}, month = {sep}, publisher = {Duke University Press}, volume = {3}, number = {3}, author = {Garrett Birkhoff}, title = {Rings of sets}, journal = {Duke Mathematical Journal} }