RT Journal Article SR Electronic T1 Cervical plexus and greater occipital nerve blocks: controversies and technique update JF Regional Anesthesia & Pain Medicine JO Reg Anesth Pain Med FD BMJ Publishing Group Ltd SP 623 OP 626 DO 10.1136/rapm-2018-100261 VO 44 IS 6 A1 Roy A Greengrass A1 Samer Narouze A1 Thomas F Bendtsen A1 Admir Hadzic YR 2019 UL http://rapm.bmj.com/content/44/6/623.abstract AB