1. L. Danzer, B. Grünbaum, and V. Klee, The Helly theorem [Russian translation], Mir, Moscow (1968).
2. V. G. Boltyanskii and I. M. Yaglom, Convex Figures [in Russian], Gosudarstvennoe Izdatel'stvo Tekhnikoteoreticheskoi Literatury, Moscow (1951).
3. H. Steinhaus, ?Sur la division des ensembles de l'espace par les plans et des ensembles plans par les cercles,? Fund. Math.,33, 245?263 (1945).
4. B. H. Neumann, ?On an invariant of plane regions and mass distributions,? J. London Math. Soc.,20, 576?582 (1945).
5. R. Rado, ?A theorem on general measures,? J. London Math. Soc.,22, 291?300 (1947).