Sven Hammarling Nicholas J. Higham Craig Lucas LAPACK-Style Codes for Pivoted Cholesky and <i>QR</i> Updating. 137-146 2006 conf/para/2006 PARA http://dx.doi.org/10.1007/978-3-540-75755-9_17 db/conf/para/para2006.html#HammarlingHL06