@article{ZNSL_2012_409_a0,
     author = {V. M. Babich},
     title = {Formal power series and their applications to mathematical theory of diffraction},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {5--16},
     year = {2012},
     volume = {409},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_2012_409_a0/}
}