@article{10_1007_s10492_007_0012_7,
     author = {Korotov, Sergey},
     title = {Two-sided a posteriori error estimates for linear elliptic problems with mixed boundary conditions},
     journal = {Applications of Mathematics},
     pages = {235--249},
     publisher = {mathdoc},
     volume = {52},
     number = {3},
     year = {2007},
     doi = {10.1007/s10492-007-0012-7},
     mrnumber = {2316154},
     zbl = {1164.65485},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.1007/s10492-007-0012-7/}
}