The Math Academy Online/ Platonic Realms website was initiated by a small group of math and math education graduate students. It boats a daily viewer ship of several thousands math students, educators, researchers, and amateurs from around the world.
They aim to provide educators and students high-quality mathematical content for secondary-school and college students. This content is free, motivational, and instructional. The Platonic Realms Homepage delivers fresh math humor, quotes, historical notes, and mathematical challenges every day. Its prime Math Encyclopedia is approaching 1000 entries, with dozen extended articles. The Interactive Quotes Database is fully data-driven, allowing searches by author, topic, and key-phrase. The MiniTexts on such diverse topics as Math Anxiety and the Art of MC Escher have received world-wide recognition, and they present foundational and popular mathematics topics at an introductory level. The Encyclopedia is designed to be browsed alphabetically. Enter the letters in the box, then the level you are looking for, and then deselect the include topics. 
