@inproceedings{Feder,
    doi = {10.1109/lics.2003.1210071},
    url = {https://doi.org/10.1109%2Flics.2003.1210071},
    publisher = {{IEEE} Comput. Soc},
    author = {T. Feder and M.Y. Vardi},
    title = {Homomorphism closed vs. existential positive},
    booktitle = {18th Annual {IEEE} Symposium of Logic in Computer Science, 2003. Proceedings.}
}

@inproceedings{Feder, doi = {10.1109/lics.2003.1210071}, url = {https://doi.org/10.1109%2Flics.2003.1210071}, publisher = {{IEEE} Comput. Soc}, author = {T. Feder and M.Y. Vardi}, title = {Homomorphism closed vs. existential positive}, booktitle = {18th Annual {IEEE} Symposium of Logic in Computer Science, 2003. Proceedings.} }