Alan George Michael T. Heath Esmond G. Ng Joseph W. H. Liu Symbolic Cholesky factorization on a local-memory multiprocessor. 85-95 1987 5 Parallel Computing 1-2 http://dx.doi.org/10.1016/0167-8191(87)90009-3 db/journals/pc/pc5.html#GeorgeHNL87