RT Journal Article SR Electronic T1 Ultrasound-guided maxillary nerve block via the pterygopalatine fossa: maxillary artery is the key JF Regional Anesthesia & Pain Medicine JO Reg Anesth Pain Med FD BMJ Publishing Group Ltd SP rapm-2020-101400 DO 10.1136/rapm-2020-101400 A1 Xiachuan Qin A1 Xisheng Xie YR 2020 UL http://rapm.bmj.com/content/early/2020/06/09/rapm-2020-101400.abstract AB