@article{MM2_1976__19_154409,
     author = {Robert Schumacher},
     title = {Zur {Minimalit\"at} {Trigonometrischer} {Polynomoperatoren.}},
     journal = {Manuscripta mathematica},
     pages = {133--142},
     publisher = {mathdoc},
     volume = {19},
     year = {1976},
     zbl = {0328.42001},
     url = {http://geodesic.mathdoc.fr/item/MM2_1976__19_154409/}
}