@article{10_4064_ap_18_3_263_269,
     author = {W. D\"uck},
     title = {Entwicklung nach {Eigenfunktionen} nat\"urlicher {Eigenwertprobleme}},
     journal = {Annales Polonici Mathematici},
     pages = {263--269},
     publisher = {mathdoc},
     volume = {18},
     number = {3},
     year = {1966},
     doi = {10.4064/ap-18-3-263-269},
     language = {de},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-18-3-263-269/}
}