Trigger points is another health topic that's difficult to research. Nevertheless, trigger point identification and treatment can provide rapid relief for both long-term and frequently recurring pain.
The best information source I've found so far is Clair Davies's excellent book The Trigger Point Therapy Workbook: Your Self-Treatment Guide for Pain Relief (available from Amazon or other online bookshops).
This comprehensive manual is often cited as the definitive reference by physiotherapists. And whenever I decide to re-read a particular topic I invariably discover a little more about the root causes, symptoms and treatments.