@article{IM2_1995_59_5_a4,
     author = {L. I. Kamynin and B. N. Khimchenko},
     title = {On a~weak extremum principle for a~second-order elliptic system},
     journal = {Izvestiya. Mathematics},
     pages = {949--961},
     year = {1995},
     volume = {59},
     number = {5},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1995_59_5_a4/}
}