RT Journal Article SR Electronic T1 Systolic time intervals and impedance cardiography. JF British Heart Journal JO Heart FD BMJ Publishing Group Ltd and British Cardiovascular Society SP 253 OP 254 DO 10.1136/hrt.41.2.253 VO 41 IS 2 A1 D H Spodick YR 1979 UL http://heart.bmj.com/content/41/2/253.abstract AB