@article{MZM_1969_6_2_a11,
     author = {Yu. G. Dutkevich},
     title = {Diameter of the set of midpoints of chords of a~bounded closed set},
     journal = {Matemati\v{c}eskie zametki},
     pages = {233--236},
     publisher = {mathdoc},
     volume = {6},
     number = {2},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1969_6_2_a11/}
}