(This book is written using XMLmind_XML_Editor Standard Edition (approximately what you see is what you get), using oxygen to arrange the output. The former is free and has functional constraints, while the latter is the D version, which has relatively complete documentation and output functions, but editing documents is a bit embarrassing for an amateur like me. There are a lot of people on the Internet that introduce the output environment of their own equipment. If my method goes against my own values, I can also use the former plus the output environment of my own equipment.)