@article{NUMA_1986__48_133086,
     author = {A. van der Sluis and H.A. van der Vorst},
     title = {The {Rate} of {Convergence} of {Conjugate} {Gradients.}},
     journal = {Numerische Mathematik},
     pages = {543--560},
     year = {1986},
     volume = {48},
     zbl = {0596.65015},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1986__48_133086/}
}