@article{MZ_1977__153_172489,
     author = {Jan-Erik. Andersson and Tord Ganelius},
     title = {The {Degree} of {Approximation} by {Rational} {Functions} with {Fixed} {Poles.}},
     journal = {Mathematische Zeitschrift},
     pages = {161--166},
     publisher = {mathdoc},
     volume = {153},
     year = {1977},
     zbl = {0331.30028},
     url = {http://geodesic.mathdoc.fr/item/MZ_1977__153_172489/}
}