@article{Halava_2006,
    doi = {10.1051/ita:2006039},
    url = {https://doi.org/10.1051%2Fita%3A2006039},
    year = {2006},
    month = {oct},
    publisher = {{EDP} Sciences},
    volume = {40},
    number = {4},
    pages = {551--557},
    author = {Vesa Halava and Tero Harju},
    title = {Undecidability of infinite post correspondence problem for instances of Size 9},
    journal = {{RAIRO} - Theoretical Informatics and Applications}
}

@article{Halava_2006, doi = {10.1051/ita:2006039}, url = {https://doi.org/10.1051%2Fita%3A2006039}, year = {2006}, month = {oct}, publisher = {{EDP} Sciences}, volume = {40}, number = {4}, pages = {551--557}, author = {Vesa Halava and Tero Harju}, title = {Undecidability of infinite post correspondence problem for instances of Size 9}, journal = {{RAIRO} - Theoretical Informatics and Applications} }