@article{MZ_1972__124_171682,
     author = {Hansgeorg Jeggle},
     title = {\"Uber die {Approximation} von linearen {Glechungen} zweiter {Art} und {Eigenwertproblemen} in {Banach-R\"aumen.}},
     journal = {Mathematische Zeitschrift},
     pages = {319--342},
     publisher = {mathdoc},
     volume = {124},
     year = {1972},
     zbl = {0229.47010},
     url = {http://geodesic.mathdoc.fr/item/MZ_1972__124_171682/}
}