@inproceedings{Rounds_1969,
    doi = {10.1145/800169.805428},
    url = {https://doi.org/10.1145%2F800169.805428},
    year = {1969},
    publisher = {{ACM} Press},
    author = {William C. Rounds},
    title = {Context-free grammars on trees},
    booktitle = {Proceedings of the first annual {ACM} symposium on Theory of computing  - {STOC} {\textquotesingle}69}
}

@inproceedings{Rounds_1969, doi = {10.1145/800169.805428}, url = {https://doi.org/10.1145%2F800169.805428}, year = {1969}, publisher = {{ACM} Press}, author = {William C. Rounds}, title = {Context-free grammars on trees}, booktitle = {Proceedings of the first annual {ACM} symposium on Theory of computing - {STOC} {\textquotesingle}69} }