A few useful resources on notes, particularly evergreen-style notes:

• How to Take Smart Notes, Sönke Ahrens
  • This book discusses Niklas Luhmann's Zettelkasten system and how you can use it to research and study.
• How to Make a Complete Map of Every Thought You Think, Lion Kimbro
  • Ebook about using a series of three-ring binders to take notes on and organize all your thoughts. Focuses on mind-maps, hierarchical subject divisions, and indexes as the organizing principles. It is very stream-of-consciousness, so will probably not appeal to someone who wants a straightforward treatment of note-taking techniques, but if you like seeing how other people operate their note-taking practices and thinking through system design, you might appreciate it more this way.

If you're interested in Zettelkasten in particular, check out my bibliography on the topic.