@article{700935,
     title = {On an inequality concerning Cartesian multiplication},
     booktitle = {General Topology and its Relations to Modern Analysis and Algebra},
     series = {GDML\_Books},
     publisher = {Academia Publishing House of the Czechoslovak Academy of Sciences},
     address = {Praha},
     year = {1962},
     pages = {[258]-259},
     mrnumber = {MR0175792},
     zbl = {0111.18403},
     url = {http://dml.mathdoc.fr/item/700935}
}

Kurepa, D. On an inequality concerning Cartesian multiplication, dans General Topology and its Relations to Modern Analysis and Algebra, GDML_Books,  (1962), pp. [258]-259. http://gdmltest.u-ga.fr/item/700935/