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 rapm-2018-100261 DO 10.1136/rapm-2018-100261 A1 Greengrass, Roy A A1 Narouze, Samer A1 Bendtsen, Thomas F A1 Hadzic, Admir YR 2019 UL http://rapm.bmj.com/content/early/2019/03/12/rapm-2018-100261.abstract AB