@article{DAN_1991_317_5_a1,
     author = {M. D. Bronshtein and A. S. Cherevatskii},
     title = {A variational method for solving boundary value problems for ordinary differential equations},
     journal = {Doklady Akademii Nauk},
     pages = {1037--1041},
     publisher = {mathdoc},
     volume = {317},
     number = {5},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1991_317_5_a1/}
}