@article{NUMA_1986__48_133085,
     author = {Stephan Ruscheweyh and Roland Freund},
     title = {On a {Class} of {Chebyshev} {Approximation} {Problems} {Which} {Arise} in {Connection} with a {Conjugate} {Gradient} {Type} {Method.}},
     journal = {Numerische Mathematik},
     pages = {525--542},
     publisher = {mathdoc},
     volume = {48},
     year = {1986},
     zbl = {0611.65016},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1986__48_133085/}
}