Rademacher functionsRademacher functions have been the subject of intense research since, in 1922, Hans Rademacher introduced them as an orthogonal system of functions in [142]. He soon wrote a sequel on the completion of this system but unfortunately he was discouraged from publishing it. Meanwhile, J. L. Walsh [169] in 1923, independently completed the system and published a paper containing much of Rademacher’s work. Rademacher never published his second paper, which, for many years, was considered to be permanently lost but in 1979, the paper was miraculously unearthed.