Fred G. Gustavson John K. Reid Jerzy Wasniewski Algorithm 865: Fortran 95 subroutines for Cholesky factorization in block hybrid format. 8 2007 33 ACM Trans. Math. Softw. 1 http://doi.acm.org/10.1145/1206040.1206048 db/journals/toms/toms33.html#GustavsonRW07