A paper by Dr Piotr Wozniak published in Feb 1999.
This was referenced by the talk on the Anki Cloze Overlapper as a "pretty standard paper if you want to know how to create flash cards effectively". It does seem to crop up everywhere, but that's where I first took note.
Pitr Wozniak (author of Super Memo) has been iterating these rules since 1999. 1999 Article 
The latest update to these rules was in 2018. History
## 20 Rules of Formulating Knowledge
1. Don't learn things that you do not understand
2. Learn before you memorize
3. Start from basics before going into complexities
4. Keep questions simple
5. Pictures assist memory
6. Learn mnemonic techniques, e.g. peg lists
7. Avoid lists, sets and enumerations. They can be tackled with cloze deletion. See Using Decompose in Incremental Reading.
8. Personalize and provide examples
9. Cloze deletion is fast and has a great mnemonic power
10. Use redundancy (similar items asking similar questions from different angles)
11. Use references
12. Building comprehension may be part of the learning process, and creating cloze deletions on poorly understood phrases is acceptable
13. Learning and memorization may occur in parallel (see: video)
14. Early in the learning process, items may be complex. They get simplified incrementally depending on knowledge priority, and the available time
15. Multiple cloze deletions on different formulations of the same statement may often substitute for mnemonic techniques (see: Knowledge darwinism)
16. Lists, sets, and enumerations can be easily tackled with cloze deletion (see: video)
17. For personalization, add your own stories to texts that you learn. Elaborate creatively
18. A simple and universal litmus test for a good formulation is pleasure of learning. Each time you see a drop in pleasure, come back to this text and see if you can find a rule violation that might be responsible for the decline in fun.
19. We should strive at maximum applicability of knowledge.
20. Simplicity: In representing knowledge, we should always strive at formulating atomic memories set in a good context of comprehension.