The Wiener Wintner ergodic theorem is a strengthening of Birkhoff pointwise ergodic theorem.

... 9810244398 . [ 3 ] D. Berend : " Joint ergodicity and mixing ” , J. d'Anal . Math . , 45 , ( 1985 ) , 255-284 . [ 4 ] J. Coquet , T. Kamae and M. Mendes - France : " Sur la mesure spectrale de certaines suites arithmetiques ” , Bull ...