@article{NUMA_1975__25_132369,
     author = {W. Knauff and R. Kre{\ss}},
     title = {Optimale {Approximation} mit {Nebenbedingungen} an lineare {Funktionale} auf periodischen {Funktionen.}  -  {Optimal} {Approximation} with {Side} {Conditions} to {Linear} {Functionals} on {Periodic} {Functions.}},
     journal = {Numerische Mathematik},
     pages = {149--152},
     publisher = {mathdoc},
     volume = {25},
     year = {1975},
     zbl = {0307.65032},
     url = {http://geodesic.mathdoc.fr/item/NUMA_1975__25_132369/}
}