@article{DAN_1981_256_1_a3,
     author = {V. K. Isaev},
     title = {The {Pontrjagin} maximum principle and $\Pi$-splines},
     journal = {Doklady Akademii Nauk},
     pages = {22--25},
     year = {1981},
     volume = {256},
     number = {1},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1981_256_1_a3/}
}