@article{MAN_1966__165_161418,
     author = {W. TUTSCHKE},
     title = {Zur {Theorie} der parameterabh\"angigen {Differentialformen.} {II.} {Lineare} {Differentialoperatoren} zweiter {Ordnung} und zugeordnetes {Koeffizientendifferential.}},
     journal = {Mathematische Annalen},
     pages = {31--35},
     publisher = {mathdoc},
     volume = {165},
     year = {1966},
     zbl = {0144.35604},
     url = {http://geodesic.mathdoc.fr/item/MAN_1966__165_161418/}
}