I remember reading long ago that of all of the hundreds of books that Isaac Asimov wrote, his least favourite was his set of science ABC books. He found it maddening to have to omit vocabulary absolutely central to the topic because it happened to start with the same letter as an even more important word. "S", I recall, posed a big problem when writing his ABC's of Space. Should he pick "star", "Saturn", "satellite", "solar flares", or "space" itself? Meanwhile, other letters offered a dearth of relevant, interesting words so he had to take a concept from a doublebooked letter and pin it to the lacking letter with a lesser word. Oh, Asimov, I feel your pain!