@article{Brown_1964,
    doi = {10.4153/cjm-1964-058-7},
    url = {https://doi.org/10.4153%2Fcjm-1964-058-7},
    year = {1964},
    publisher = {Canadian Mathematical Society},
    volume = {16},
    pages = {572--577},
    author = {W. G. Brown and W. T. Tutte},
    title = {On the Enumeration of Rooted Non-Separable Planar Maps},
    journal = {Canadian Journal of Mathematics}
}

@article{Brown_1964, doi = {10.4153/cjm-1964-058-7}, url = {https://doi.org/10.4153%2Fcjm-1964-058-7}, year = {1964}, publisher = {Canadian Mathematical Society}, volume = {16}, pages = {572--577}, author = {W. G. Brown and W. T. Tutte}, title = {On the Enumeration of Rooted Non-Separable Planar Maps}, journal = {Canadian Journal of Mathematics} }