@incollection{Vorobyov_1998,
    doi = {10.1007/bfb0055810},
    url = {https://doi.org/10.1007%2Fbfb0055810},
    year = {1998},
    publisher = {Springer Berlin Heidelberg},
    pages = {597--606},
    author = {Sergei Vorobyov},
    title = {{$\forall$$\exists$-Equational theory of context unification is {$\pi$}10-hard}},
    booktitle = {Mathematical Foundations of Computer Science 1998}
}

@incollection{Vorobyov_1998, doi = {10.1007/bfb0055810}, url = {https://doi.org/10.1007%2Fbfb0055810}, year = {1998}, publisher = {Springer Berlin Heidelberg}, pages = {597--606}, author = {Sergei Vorobyov}, title = {{$\forall$$\exists$-Equational theory of context unification is {$\pi$}10-hard}}, booktitle = {Mathematical Foundations of Computer Science 1998} }