@article{10_4064_ap_2_1_77_96,
     author = {A. Krzywicki and J. Rzewuski and J. Zamorski and A. Zi\k{e}ba},
     title = {Non-local problems in the calculus of variations {(I)}},
     journal = {Annales Polonici Mathematici},
     pages = {77--96},
     publisher = {mathdoc},
     volume = {2},
     number = {1},
     year = {1955},
     doi = {10.4064/ap-2-1-77-96},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/ap-2-1-77-96/}
}