@article{JDM_1935__45_146082,
     author = {K Friedrichs},
     title = {Spektraltheorie linearer {Differentialoperatoren.}},
     journal = {Jahresbericht der Deutschen Mathematiker-Vereinigung},
     pages = {181--193},
     publisher = {mathdoc},
     volume = {45},
     year = {1935},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/JDM_1935__45_146082/}
}