@article{10_4064_ap_65_2_139_150,
     author = {Jan Popio{\l}ek},
     title = {On boundary-value problems for partial differential equations of order higher than two},
     journal = {Annales Polonici Mathematici},
     pages = {139--150},
     publisher = {mathdoc},
     volume = {65},
     number = {2},
     year = {1996},
     doi = {10.4064/ap-65-2-139-150},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-65-2-139-150/}
}