@article{SM_1973_19_3_a4,
     author = {N. N. Nekhoroshev},
     title = {Stable lower estimates for smooth mappings and for gradients of smooth function},
     journal = {Sbornik. Mathematics},
     pages = {425--467},
     publisher = {mathdoc},
     volume = {19},
     number = {3},
     year = {1973},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1973_19_3_a4/}
}