  Consider the one-parameter generalizations of the logarithmic and exponential
functions which are obtained from the integration of non-symmetrical
hyperboles. These generalizations coincide to the one obtained in the context
of non-extensive thermostatistics. We show that these functions are suitable to
describe and unify the great majority of continuous growth models, which we
briefly review. Physical interpretation to the generalization function
parameter is given for the Richards' model, which has an underlying microscopic
model to justify it.
