@article{DAN_1989_306_5_a9,
     author = {Ya. Z. Tsypkin and A. S. Poznyak},
     title = {A generalized method of instrumental variables in problems of the},
     journal = {Doklady Akademii Nauk},
     pages = {1068--1072},
     publisher = {mathdoc},
     volume = {306},
     number = {5},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1989_306_5_a9/}
}