“…The first limit T 1=2 > 3 × 10 15 yr was made with 124 Sn in Geiger counters (Fireman, 1948). Follow-on direct experiments (Fireman, 1949;Lawson, 1951;Fireman and Schwarzer, 1952;Fremlin and Walters, 1952;Kalkstein and Libby, 1952;Pearce and Darby, 1952;McCarthy, 1953McCarthy, , 1955 incorporated proportional counters, scintillators, Wilson chambers, and nuclear emulsions using several isotopes and included some positive claims (Fireman, 1949;Fremlin and Walters, 1952;McCarthy, 1953McCarthy, , 1955 that were disproved in more sensitive experiments, a theme that has repeated itself throughout the history of double-beta decay experiments; see Tretyak (2011). Meanwhile, geochemical searches Reynolds, 1949, 1950;Levine, Ghiorso, and Seaborg, 1950), which are sensitive only to the combination of 0νββ and 2νββ decay and not to each of them separately, yielded strong limits, as well as the first observation of ββ decay of 130 Te with a half-life of 1.4 × 10 21 yr (Inghram and Reynolds, 1950), which is consistent with the rate of Goeppert-Mayer's 2νββ decay.…”