@article{DAN_1991_320_5_a0,
     author = {D. E. Akbarov and V. I. Ivanenko},
     title = {Extremal problems for equations of {Hammerstein} type},
     journal = {Doklady Akademii Nauk},
     pages = {1033--1036},
     year = {1991},
     volume = {320},
     number = {5},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1991_320_5_a0/}
}