@misc{ZNSL_1969_15_a0,
     title = {Preface},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {5--8},
     year = {1969},
     volume = {15},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1969_15_a0/}
}