([Wikipedia](https://en.wikipedia.org/wiki/Zettelkasten)) A method of notetaking on small, numbered, and interlinked slips of paper, arguably popularized by Niklas Luhmann in a 1981 [essay](https://ckrybus.com/static/papers/luhmann1981.pdf) (the [english translation](https://luhmann.surge.sh/communicating-with-slip-boxes) leaves a little to be desired). It seeks to establish a "communicating partner", nowadays often referred to as a "[[A second brain]]".