@article{SM_1990_65_1_a8,
     author = {B. S. Pavlov and A. A. Shushkov},
     title = {The theory of extentions and zero-radius potentials with internal structure},
     journal = {Sbornik. Mathematics},
     pages = {147--184},
     publisher = {mathdoc},
     volume = {65},
     number = {1},
     year = {1990},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1990_65_1_a8/}
}