RT Journal Article SR Electronic T1 Extracting smoking data from GP electronic health records JF British Journal of General Practice JO Br J Gen Pract FD British Journal of General Practice SP 58 OP 59 DO 10.3399/bjgp21X714701 VO 71 IS 703 A1 Nigel J Masters YR 2021 UL http://bjgp.org/content/71/703/58.3.abstract AB