@article{MZM_2001_70_2_a7,
     author = {A. I. Perov},
     title = {Jorke's {Theorem} and {Wirtinger's} {Inequality}},
     journal = {Matemati\v{c}eskie zametki},
     pages = {237--245},
     publisher = {mathdoc},
     volume = {70},
     number = {2},
     year = {2001},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_2001_70_2_a7/}
}