Recommended energies are given for reference gamma rays in the decay o
f Eu-156 and Tb-156 in the photon-energy range 0.8-1.2 MeV with errors
of a few electron volts, which are derived from data on gamma transit
ions from levels of Gd-156 occurring in (n gamma) reactions and the de
cays of Eu-156 and Tb-156.