RT Journal Article SR Electronic T1 Disparity between studies of the stability of BNP in blood: comparison of endogenous and exogenous peptide JF Heart JO Heart FD BMJ Publishing Group Ltd and British Cardiovascular Society SP 212 OP 213 DO 10.1136/hrt.81.2.212 VO 81 IS 2 A1 D R Murdoch A1 J Byrne A1 R Farmer A1 J J Morton YR 1999 UL http://heart.bmj.com/content/81/2/212.abstract AB