A quick note to the personal knowledge management fanatics: Niklas Luhmann positively did NOT invent the Zettelkasten. The idea predates him by quite a bit and had even earlier forms. He’s also not the only significant example.

https://boffosocko.com/2021/07/03/differentiating-online-variations-of-the-commonplace-book-digital-gardens-wikis-zettlekasten-waste-books-florilegia-and-second-brains/