Peripheral nerve blocks and trigger point injections in headache management -- a systematic review and suggestions for future research. - Ashkenazi A; Blumenfeld A; Napchan U; Narouze S; Grosberg B; Nett R; DePalma T; Rosenthal B; Tepper S; Lipton RB; Headache Center of Southern California, Encinitas, CA, USA (Headache: The Journal of Head & Face Pain, 2010)