A manual for writers of research papers, theses, and dissertations, 7th edition - Kate L. Turabian 2007

Re-sort your notes
Engaging sources
Part I. Research and writing: from planning to production

If none of that helps, try re-sorting your notes. When you first selected keywords for your notes, you identified general concepts that could organize not just your evidence but your thinking. If you chose keywords representing those concepts carefully, you can re-sort your notes in different ways to get a new slant on your material. If your keywords no longer seem relevant, review your notes to create new ones and reshuffle again.