@article{Almkvist_1990,
    doi = {10.1016/s0747-7171(08)80159-9},
    url = {https://doi.org/10.1016%2Fs0747-7171%2808%2980159-9},
    year = {1990},
    month = {dec},
    publisher = {Elsevier {BV}},
    volume = {10},
    number = {6},
    pages = {571--591},
    author = {Gert Almkvist and Doron Zeilberger},
    title = {The method of differentiating under the integral sign},
    journal = {Journal of Symbolic Computation}
}

@article{Almkvist_1990, doi = {10.1016/s0747-7171(08)80159-9}, url = {https://doi.org/10.1016%2Fs0747-7171%2808%2980159-9}, year = {1990}, month = {dec}, publisher = {Elsevier {BV}}, volume = {10}, number = {6}, pages = {571--591}, author = {Gert Almkvist and Doron Zeilberger}, title = {The method of differentiating under the integral sign}, journal = {Journal of Symbolic Computation} }