@article{MAN_1966__163_161378,
     author = {A. DOUGLIS},
     title = {On {Weak} {Solutions} of {Non-Linear} {Partial} {Differential} {Equations} with {Real} {Characteristics.}},
     journal = {Mathematische Annalen},
     pages = {351--358},
     publisher = {mathdoc},
     volume = {163},
     year = {1966},
     zbl = {0137.28904},
     url = {http://geodesic.mathdoc.fr/item/MAN_1966__163_161378/}
}