RT Journal Article SR Electronic T1 Cervical erector spinae versus retrolaminar plane block as an alternative to classical interscalene block JF Regional Anesthesia & Pain Medicine JO Reg Anesth Pain Med FD BMJ Publishing Group Ltd SP rapm-2021-102831 DO 10.1136/rapm-2021-102831 A1 Ban C H Tsui A1 Hesham Elsharkawy YR 2021 UL http://rapm.bmj.com/content/early/2021/05/23/rapm-2021-102831.abstract AB