Voir la notice de l'article provenant de la source Hellenic Digital Mathematics Library
@article{EUG_1989__21_a7, author = {A. D. Tzouvaras}, title = {A {non-Standard} {Characterization} of the norm of free {Ultrafilters}}, journal = {E\ensuremath{\upsilon}\ensuremath{\kappa}\ensuremath{\lambda}\ensuremath{\varepsilon}\ensuremath{\acute\iota}\ensuremath{\delta}\ensuremath{\eta}\ensuremath{\varsigma} \ensuremath{\Gamma} }, pages = {81-85}, publisher = {mathdoc}, volume = {21}, year = {1989}, language = {gr}, url = {http://geodesic.mathdoc.fr/item/EUG_1989__21_a7/} }
A. D. Tzouvaras. A non-Standard Characterization of the norm of free Ultrafilters. Ευκλείδης Γ , Tome 21 (1989), p. 81-85. http://geodesic.mathdoc.fr/item/EUG_1989__21_a7/