@article{10_1007_s10492_004_6404_z,
     author = {Proch\'azka, Petr and \v{S}ejnoha, Ji\v{r}{\'\i}},
     title = {Extended {Hashin-Shtrikman} variational principles},
     journal = {Applications of Mathematics},
     pages = {357--372},
     publisher = {mathdoc},
     volume = {49},
     number = {4},
     year = {2004},
     doi = {10.1007/s10492-004-6404-z},
     mrnumber = {2076490},
     zbl = {1099.74054},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.1007/s10492-004-6404-z/}
}