Covariances between experimental data are as significant as variances both
in the evaluation of uncertainties and to perform statistical tests. If sta
ndard data are used in calibrations, covariances must be taken into account
. Covariances are also necessary in order to update values every time when
new data are obtained. In this paper we determined covariances between the
most important gamma-ray energies for use in Ge-semiconductor detectors cal
ibration recently published by Helmer and van der Leun (Nucl. Instr. Meth.
A 450 (2000) 35). (C) 2001 Elsevier Science B.V. All rights reserved.