Some of the structure in Kaiser's system was built into relationships on guide cards. While not exactly hub notes, they did provide links to other areas of the system in addition to synonyms under which materials could be found including broader terms, narrower terms, and related terms often seen in library information systems.

reply to u/IvanCyb at https://www.reddit.com/r/antinet/comments/15eljnf/how_do_you_refer_from_and_to_multiple_sources/

Usually if I find a quote somewhere, I'll try to track down the original source, check the context and excerpt it from the original. If it's something mission critical, I might note that it was excerpted and used in other sources and whether it was well excerpted for their case or not. Sometimes, quoting can also help to make a solid case about the influence a work had and notes on that can be a useful thing. If I make multiple notes about the same sort of idea, that's fine, though I typically try to file them all next to each other for easy consultation and comparison, if necessary. As an example, I have quotes from multiple sources about note taking indicating that one should only write on one side of a(n index) card. Some quote earlier sources, some state it without attribution, some say they've learned to do so over time and with experience. Some give reasons why and some don't. The only way to track these practices over time is to note them all together for comparing and contrasting. It wasn't until I'd seen the third mention that I realized the practice was an interesting/important one and worth tracking, so I had to go back and dig up the originals which I had written briefly on their bibliographic cards with page numbers, so it made things easier to create main cards out of them. Because they're all stored together, there's only one index entry for them (for the first one), under "note taking" with the subheading "write only on one side". Alternately I might have made a single note card about the idea of the practice and created a list with pointers of those who used it (or didn't) and links to the sources where I originally found them. Do what makes most sense for you for tracking based on your own situation and needs. You may also find that these things happen frequently when doing literature reviews and things are repeated often within a field. Sometimes it's helpful to figure out who said a thing first and whether or not others are repeating/quoting them or coming to the same conclusion on their own. Is it a solid conclusion? What is the evidence or lack thereof? The only way to know is to start keeping track of these patterns in your reading and notes. Where and how you choose to track it in your zettelkasten is up to you. Sometimes it may be in brief notes with the original source, sometimes in a "hub note", and still others broken out into primary cards collected together.

An important update to this piece as Sascha's method evolved. Instead of using outlines to capture new notes, he started using structured notes.

I suspect the reason for this is that a system with atomic notes and structured notes is more clear cut than a system that relies on work-in-progress outlines. The main difference being that a structured note will contain only notes and not some floating, un-evolved ideas.

Interesting point where the author compares the barrier that is created between the editing and the writing mode in a wiki (which makes it more cumbersome to continue lines of thought) to the barriers that appear when you're not using the right software or conventions to structure your knowledge items, as well as to structure your knowledge items' structure.

After the need for a layer of Hub Notes a new need may emerge: to better organize the Hub Notes themselves. At this point you may want to introduce structure notes that structure sets of structured notes.

Structure notes or Hub Notes are similar to tags (or pages in Roam) in that they point to a collection of other notes (or pages in Roam). The only difference being that structure notes contain within themselves a structure which provides hierarchy and context.

There seems to be an inflection point where your initial approach to organizing your Zettelkasten starts to fail (perhaps 500-700 notes). You'll simply have too many tags to choose from.

At this point hub-like notes will be the next stage in the evolution of your Zettelkasten organization.