@article{Zizler_1973, title={On Some Extremal Problems in Banach Spaces.}, volume={32}, url={https://www.mscand.dk/article/view/11456}, DOI={10.7146/math.scand.a-11456}, journal={MATHEMATICA SCANDINAVICA}, author={Zizler, Václav}, year={1973}, month={Dec.}, pages={214–224} }