@article{DAN_1989_308_4_a6,
     author = {S. Yu. Yakovenko},
     title = {On the concept of an infinite extremal in stationary problems of},
     journal = {Doklady Akademii Nauk},
     pages = {798--802},
     publisher = {mathdoc},
     volume = {308},
     number = {4},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1989_308_4_a6/}
}