RT Journal Article SR Electronic T1 Method to Calculate Activity of a Source from Counting Rates in Single and Coincidence Photopeaks JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1043 OP 1044 VO 18 IS 10 A1 K. J. Van Damme YR 1977 UL http://jnm.snmjournals.org/content/18/10/1043.2.abstract AB