@article{DAN_1979_244_6_a5,
     author = {L. I. Kamynin and B. N. Khimchenko},
     title = {Investigations on the isotropic strict extremum principle},
     journal = {Doklady Akademii Nauk},
     pages = {1312--1316},
     publisher = {mathdoc},
     volume = {244},
     number = {6},
     year = {1979},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1979_244_6_a5/}
}