On the Spectra of Almost Periodic Functions Louis PignoSadahiro Saeki Indiana University Mathematics Journal 1976 text pdf 10.1512/iumj.1976.25.25015 10.1512/iumj.1976.25.25015 en Indiana Univ. Math. J. 25 (1976) 191 - 194 state-of-the-art mathematics http://iumj.org/access/