@article{MZ_1972__129_171822,
     author = {Johann Walter},
     title = {Absolute {Continuity} of the {Essential} {Spectrum} of - ... + q (t) without {Monotony} of q.},
     journal = {Mathematische Zeitschrift},
     pages = {83--94},
     publisher = {mathdoc},
     volume = {129},
     year = {1972},
     zbl = {0252.47043},
     url = {http://geodesic.mathdoc.fr/item/MZ_1972__129_171822/}
}