@article{MZ_1974__140_172144,
     author = {Rickleff Br\"ubach},
     title = {\"Uber die {Spektralmatrix} elliptischer {Systeme.}},
     journal = {Mathematische Zeitschrift},
     pages = {231--244},
     year = {1974},
     volume = {140},
     zbl = {0279.35066},
     url = {http://geodesic.mathdoc.fr/item/MZ_1974__140_172144/}
}