We prove F. Riesz’ inequality assuming the boundedness of the norm of the first arithmetic mean of the functions with p ≥ 2 instead of boundedness of the functions φₙ of an orthonormal system.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-bc68-0-11, author = {W. \L enski}, title = {Remark on the inequality of F. Riesz}, journal = {Banach Center Publications}, volume = {68}, year = {2005}, pages = {95-97}, zbl = {1130.42026}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-bc68-0-11} }
W. Łenski. Remark on the inequality of F. Riesz. Banach Center Publications, Tome 68 (2005) pp. 95-97. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-bc68-0-11/