In 1968 M. J. Rice pointed out that the coefficient A should vary predominantly as the square of the linear electronic specific heat coefficient γ; in particular he showed that the ratio A/γ is material independent for the pure 3d, 4d and 5d transition metals. Heavy-fermion compounds are characterized by very large values of A and γ. Kadowaki and Woods showed that A/γ is material-independent within the heavy-fermion compounds, and that it is about 25 times larger than in aforementioned transition metals.