Progressive Summarization is a note taking strategy which uses repeated visits to a document to slowly distill the article to its important parts.
The process involves five steps. 1. Start collecting documents into a note-taking system. 2. Mark important sections as bold. 3. Mark even more important parts with a highlight. The really important parts should now be bold and highlighted. 4. Summarize the article, focusing on the most important parts. These summaries would be Ever-Green Notes or Zettelkasten entries if you use either of those systems. 5. Recreate the article with new ideas and notes. This is more than a summary. You create an article based on the same ideas but entirely in your own voice and with your own insight.