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    ".. [1] T. A. Davis, Algorithm 832:  UMFPACK - an unsymmetric-pattern",
    "       multifrontal method with a column pre-ordering strategy, ACM",
    "       Trans. on Mathematical Software, 30(2), 2004, pp. 196--199.",
    "       https://dl.acm.org/doi/abs/10.1145/992200.992206",
    "",
    ".. [2] T. A. Davis, A column pre-ordering strategy for the",
    "       unsymmetric-pattern multifrontal method, ACM Trans.",
    "       on Mathematical Software, 30(2), 2004, pp. 165--195.",
    "       https://dl.acm.org/doi/abs/10.1145/992200.992205",
    "",
    ".. [3] T. A. Davis and I. S. Duff, A combined unifrontal/multifrontal",
    "       method for unsymmetric sparse matrices, ACM Trans. on",
    "       Mathematical Software, 25(1), 1999, pp. 1--19.",
    "       https://doi.org/10.1145/305658.287640",
    "",
    ".. [4] T. A. Davis and I. S. Duff, An unsymmetric-pattern multifrontal",
    "       method for sparse LU factorization, SIAM J. Matrix Analysis and",
    "       Computations, 18(1), 1997, pp. 140--158.",
    "       https://doi.org/10.1137/S0895479894246905T."
  ],
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