@article{Toyama_1987,
    doi = {10.1016/0020-0190(87)90122-0},
    url = {https://doi.org/10.1016%2F0020-0190%2887%2990122-0},
    year = {1987},
    month = {may},
    publisher = {Elsevier {BV}},
    volume = {25},
    number = {3},
    pages = {141--143},
    author = {Yoshihito Toyama},
    title = {Counterexamples to termination for the direct sum of term rewriting systems},
    journal = {Information Processing Letters}
}

@article{Toyama_1987, doi = {10.1016/0020-0190(87)90122-0}, url = {https://doi.org/10.1016%2F0020-0190%2887%2990122-0}, year = {1987}, month = {may}, publisher = {Elsevier {BV}}, volume = {25}, number = {3}, pages = {141--143}, author = {Yoshihito Toyama}, title = {Counterexamples to termination for the direct sum of term rewriting systems}, journal = {Information Processing Letters} }