. . . . . . . "http://www.iso.org/iso/catalogue_detail?csnumber=31895"^^ . . . . . . . . . . . . . . . "\\(\\tau\\)"^^ . . . . "\\(\\tau = \\frac{1}{\\lambda}\\), where \\(\\lambda\\) is the decay constant."^^ . . . . . "Mean Lifetime"@en . . . "The \"Mean Lifetime\" is the average length of time that an element remains in the set of discrete elements in a decaying quantity, \\(N(t)\\)."^^ . . . . . "http://en.wikipedia.org/wiki/Exponential_decay"^^ . . . . . .