@article{DAN_1970_191_1_a6,
     author = {V. A. Rokhlin},
     title = {The normal {Euler} numbers of the projective plane and {Klein} bottle in four-dimensional {Euclidean} space},
     journal = {Doklady Akademii Nauk},
     pages = {27--29},
     publisher = {mathdoc},
     volume = {191},
     number = {1},
     year = {1970},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1970_191_1_a6/}
}