@article{MMO_1968_18_a9,
     author = {A. D. Ioffe and V. M. Tikhomirov},
     title = {Extension of variational problems},
     journal = {Trudy Moskovskogo matemati\v{c}eskogo ob\^{s}estva},
     pages = {187--246},
     publisher = {mathdoc},
     volume = {18},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MMO_1968_18_a9/}
}