“…Several authors (Verheijke 1964, Snyder 1967, Trombka 1971, Holmberg and Rieppo 1973, Holmberg et a1 1973a, b, Rieppo 1974, 1976, Rieppo et a1 1975 have calculated efficiency values for low-energy y rays. The calculations of efficiency values have been carried out for different NaI(Tl) detectors with different source media.…”