@article{Goldberg_2021,
    doi = {10.1016/j.jcss.2021.05.004},
    url = {https://doi.org/10.1016%2Fj.jcss.2021.05.004},
    year = {2021},
    month = {dec},
    publisher = {Elsevier {BV}},
    volume = {122},
    pages = {34--62},
    author = {Paul W. Goldberg and Alexandros Hollender},
    title = {The Hairy Ball problem is {PPAD}-complete},
    journal = {Journal of Computer and System Sciences}
}

@article{Goldberg_2021, doi = {10.1016/j.jcss.2021.05.004}, url = {https://doi.org/10.1016%2Fj.jcss.2021.05.004}, year = {2021}, month = {dec}, publisher = {Elsevier {BV}}, volume = {122}, pages = {34--62}, author = {Paul W. Goldberg and Alexandros Hollender}, title = {The Hairy Ball problem is {PPAD}-complete}, journal = {Journal of Computer and System Sciences} }