@article{MOMA_1979__87_177903,
     author = {F. Schurer and F.W. Steutel},
     title = {On the {Degree} of {Approximation} by the {Operators} of de la {Vall\'ee} {Poussin.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {53--64},
     publisher = {mathdoc},
     volume = {87},
     year = {1979},
     zbl = {0371.41010},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1979__87_177903/}
}