@article{SM_1974_22_1_a4,
     author = {B. V. Fedosov},
     title = {An analytic formula for the index of an elliptic boundary-value problem},
     journal = {Sbornik. Mathematics},
     pages = {61--90},
     year = {1974},
     volume = {22},
     number = {1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1974_22_1_a4/}
}