Tiago, I’ve started into an advanced copy of your forthcoming book and at the end of the introduction you have a footnote:

Other popular terms for such a system include Zettelkasten (meaning “slipbox” in German, coined by influential sociologist Niklas Luhmann), Memex (a word invented by American inventor Vannevar Bush), and digital garden (named by popular online creator Anne-Laure Le Cunff)

Please know that the zettelkasten and its traditions existed prior to Niklas Luhmann. He neither invented them nor coined their name. It’s a commonly repeated myth on the internet that he did and there’s ample evidence of their extensive use prior to his well known example. I’ve documented some brief history on Wikipedia to this effect should you need it: https://en.wikipedia.org/wiki/Zettelkasten

The earliest concept of a digital garden stems from Mark Bernstein’s essay Hypertext Gardens: Delightful Vistas in 1998. This torch was picked up by academic Mike Caulfield in a 2015 keynote/article The Garden and The Stream: A Technopastoral.

Anne-Laure Le Cunff’s first mention of “digital garden” was on April 21, 2020

Which occurred just after Maggie Appleton’s mention on 2020-04-15

And several days after Justin Tadlock’s article on 2020-04-17 

Before this there was Joel Hooks by at least 2020-02-04 , though he had been thinking about it in late 2019.

He was predated by Tom Critchlow on 2018-10-18 who credits Mike Caulfield’s article from 2015-10-17 as an influence.

Archive.org has versions of the phrase going back into the early 2000’s: https://web.archive.org/web/*/%22digital%20garden%22

Hopefully you’re able to make the edits prior to publication, or at least in an available errata.

For those who’ve been waiting for it to show up, the digitized version of box 9 of Niklas Luhmann’s second zettelkasten is now available online. It contains many of his notes on the zettelkasten itself.
https://niklas-luhmann-archiv.de/bestand/zettelkasten/zettel/ZK_2_NB_9-8g_V
For those in the back: Niklas Luhmann did not invent the Zettelkasten.
If this is something you have a penchant to forget there are bumper stickers now.

White bumper sticker with a cartoon image of Luhmann  with text that reads "Niklas Luhmann did not invent the zettelkasten"
 
Or if you need a mug for drinking your coffee as you process your permanent notes…
 
White coffee mug with cartoon image of Niklas Luhmann staring at the viewer
 

Does Spirit hide in the filing cabinet?

On a slip in his zettelkasten (a card catalog or filing cabinet of personal notes), entitled “Does Spirit hide in the filing cabinet?”, Niklas Luhmann wrote a note about people who came to see his system:

“People come, they see everything and nothing more than that, just like in porn movies; consequently, they leave disappointed.”

This is a telling story about people’s perception of the simplicity of the idea of a slip box (zettelkasten, card catalog, commonplace book or whatever you want to call your note taking system).

yellowed index card with the identifier 9/8,3 with almost illegible handwriting in German Niklas Luhmann, Zettelkasten II, index card no. 9/8,3

It’s also a testament to the fact that the value of a zettelkasten is in the upfront work that is required in making valuable notes and linking them. Many people end up trying out the simple looking system and then wonder why it isn’t working for them. The answer is that they’re not working for it.

Just as sex can be fun, working with a system of notes can be fun. (“Just” can be a problematic word, n’cest pas?)  In either framing, both partners need to do some work—neither necessarily the same work. The end result can be magic.

As Potter Stewart might have said, “I may not be able to define proper note taking, but I know it when I see it.”

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/