@article{ZNSL_1973_36_a6,
     author = {S. A. Popov},
     title = {Almost smooth two-dimensional submanyfolds of four-dimensional manyfolds and some link invariants},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {146--154},
     publisher = {mathdoc},
     volume = {36},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1973_36_a6/}
}