@article{Culik_1983,
    doi = {10.1016/0012-365x(83)90152-8},
    url = {https://doi.org/10.1016%2F0012-365x%2883%2990152-8},
    year = {1983},
    publisher = {Elsevier {BV}},
    volume = {43},
    number = {2-3},
    pages = {139--153},
    author = {Karel Culik and Juhani Karhumäki},
    title = {Systems of equations over a free monoid and Ehrenfeucht{\textquotesingle}s conjecture},
    journal = {Discrete Mathematics}
}

@article{Culik_1983, doi = {10.1016/0012-365x(83)90152-8}, url = {https://doi.org/10.1016%2F0012-365x%2883%2990152-8}, year = {1983}, publisher = {Elsevier {BV}}, volume = {43}, number = {2-3}, pages = {139--153}, author = {Karel Culik and Juhani Karhumäki}, title = {Systems of equations over a free monoid and Ehrenfeucht{\textquotesingle}s conjecture}, journal = {Discrete Mathematics} }