Hello, I know I am asking for advice about a very specific topic - periodic functions, almost periodic functions and quasi-periodic functions. I was hit by an idea and I need to know a few things more comprehensively about this topic !?~ :] I am aware that "periodic functions etc." isn't a course popularly taught (if at all?) so there may be a shortage of actual textbooks about it, but I should be complexly grateful if anyone could point me towards a way to acquire this knowledge in a relatively connected form. Maybe there are some monographs written on these subjects? Or is searching for bits and pieces here and there my only option of building a fairly exhaustive knowledge about these? Any input is very much appreciated; and I hope my topic is not too far off from being well-formed.