@article{Chen_2008,
    doi = {10.1145/1411509.1411511},
    url = {https://doi.org/10.1145%2F1411509.1411511},
    year = {2008},
    month = {oct},
    publisher = {Association for Computing Machinery ({ACM})},
    volume = {55},
    number = {5},
    pages = {1--19},
    author = {Jianer Chen and Yang Liu and Songjian Lu and Barry O{\textquotesingle}sullivan and Igor Razgon},
    title = {A fixed-parameter algorithm for the directed feedback vertex set problem},
    journal = {Journal of the {ACM}}
}

@article{Chen_2008, doi = {10.1145/1411509.1411511}, url = {https://doi.org/10.1145%2F1411509.1411511}, year = {2008}, month = {oct}, publisher = {Association for Computing Machinery ({ACM})}, volume = {55}, number = {5}, pages = {1--19}, author = {Jianer Chen and Yang Liu and Songjian Lu and Barry O{\textquotesingle}sullivan and Igor Razgon}, title = {A fixed-parameter algorithm for the directed feedback vertex set problem}, journal = {Journal of the {ACM}} }