@article{MZ_1989__201_4_174070,
     author = {Pietro Aiena},
     title = {On {Riesz} and {Inessential} {Operators.}},
     journal = {Mathematische Zeitschrift},
     pages = {521--528},
     publisher = {mathdoc},
     volume = {201},
     number = {4},
     year = {1989},
     zbl = {0702.47008},
     url = {http://geodesic.mathdoc.fr/item/MZ_1989__201_4_174070/}
}