Helmut Richter, Munich

Contrary to what they look like, the articles on this website are not attempts to teach but attempts to learn. A great method for learning something is to arrange it in new ways as if one were teaching, and to proofread it from time to time. I am sharing the output with the reader who is invited to make use of it – well aware that it would be still more effective for him to start from scratch collecting and compiling the material on his own.