Perhaps the disease had started out as a tiny dimple. On a man's chin it would have looked rugged and distinguished. On a woman's cheek it might have been called a "beauty mark." It was on her left breast and Abigail "Nabby" Adams wondered what it was. She had never noticed it before. Perhaps it was just another sign of age, an indicator that she was not a young woman anymore.
Here is an alphabetical list of online mathematics books, textbooks, monographs, lecture notes, and other mathematics related documents freely available on the web. I tried to select only the works in book formats, "real" books that are mainly in PDF format, so many well-known html-based mathematics web pages and online tutorials are left out.