@article{PIM_1966_N_S_06_20_a6,
     author = {L. Collatz},
     title = {Rationalle {Trigonometrische} {Tschebyscheff-Approximation} {In} {Zwei} {Variablen}},
     journal = {Publications de l'Institut Math\'ematique},
     pages = {57 },
     publisher = {mathdoc},
     volume = {_N_S_06},
     number = {20},
     year = {1966},
     url = {http://geodesic.mathdoc.fr/item/PIM_1966_N_S_06_20_a6/}
}