@article{10_4064_ap_52_1_1_17,
     author = {A. Pelczar},
     title = {Some qualitative problems in the theory of second order partial differential equations},
     journal = {Annales Polonici Mathematici},
     pages = {1--17},
     publisher = {mathdoc},
     volume = {52},
     number = {1},
     year = {1990},
     doi = {10.4064/ap-52-1-1-17},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-52-1-1-17/}
}