@article{Thatcher_1968,
    doi = {10.1007/bf01691346},
    url = {https://doi.org/10.1007%2Fbf01691346},
    year = {1968},
    month = {mar},
    publisher = {Springer Science and Business Media {LLC}},
    volume = {2},
    number = {1},
    pages = {57--81},
    author = {J. W. Thatcher and J. B. Wright},
    title = {Generalized finite automata theory with an application to a decision problem of second-order logic},
    journal = {Mathematical Systems Theory}
}

@article{Thatcher_1968, doi = {10.1007/bf01691346}, url = {https://doi.org/10.1007%2Fbf01691346}, year = {1968}, month = {mar}, publisher = {Springer Science and Business Media {LLC}}, volume = {2}, number = {1}, pages = {57--81}, author = {J. W. Thatcher and J. B. Wright}, title = {Generalized finite automata theory with an application to a decision problem of second-order logic}, journal = {Mathematical Systems Theory} }