Luhmann's description of his zettelkasten system. As he describes it, it is essentially just a collection of numbered cards, which refer to one another by number and have no top-down organization.
I read Manfred Kuehn's translation, from which quotation are taken.
Luhmann notes the bootstrapping problem for this system:
Ahrens suggests that the value of the slip-box is that you can paste together a series of notes, do some light editing, and have a draft of a publication (Ahrens2017). Luhmann does not seem to agree: