. "\\(u = \\ln(\\frac{E_0}{E})\\), where \\(E_0\\) is a reference energy."^^ . "http://www.iso.org/iso/catalogue_detail?csnumber=31895"^^ . "http://www.scribd.com/doc/51548050/149/Lethargy"^^ . "The \"Lethargy\" is a dimensionless logarithm of the ratio of the energy of source neutrons to the energy of neutrons after a collision." . . "u" . "Lethargy"@en . . .