@article{Wainer_1972,
    doi = {10.2307/2272973},
    url = {https://doi.org/10.2307%2F2272973},
    year = {1972},
    month = {jun},
    publisher = {Cambridge University Press ({CUP})},
    volume = {37},
    number = {2},
    pages = {281--292},
    author = {S. S. Wainer},
    title = {Ordinal recursion, and a refinement of the extended Grzegorczyk hierarchy},
    journal = {Journal of Symbolic Logic}
}

@article{Wainer_1972, doi = {10.2307/2272973}, url = {https://doi.org/10.2307%2F2272973}, year = {1972}, month = {jun}, publisher = {Cambridge University Press ({CUP})}, volume = {37}, number = {2}, pages = {281--292}, author = {S. S. Wainer}, title = {Ordinal recursion, and a refinement of the extended Grzegorczyk hierarchy}, journal = {Journal of Symbolic Logic} }