@article{Ladner_1975,
    doi = {10.1145/321864.321877},
    url = {https://doi.org/10.1145%2F321864.321877},
    year = {1975},
    month = {jan},
    publisher = {Association for Computing Machinery ({ACM})},
    volume = {22},
    number = {1},
    pages = {155--171},
    author = {Richard E. Ladner},
    title = {On the Structure of Polynomial Time Reducibility},
    journal = {Journal of the {ACM}}
}

@article{Ladner_1975, doi = {10.1145/321864.321877}, url = {https://doi.org/10.1145%2F321864.321877}, year = {1975}, month = {jan}, publisher = {Association for Computing Machinery ({ACM})}, volume = {22}, number = {1}, pages = {155--171}, author = {Richard E. Ladner}, title = {On the Structure of Polynomial Time Reducibility}, journal = {Journal of the {ACM}} }