Weak approximation of an invariant measure and a low boundary of the   entropy
  For a measurable map $T$ and a sequence of $T$-invariant probability measures $\mu_n$ that converges in some sense to a $T$-invariant probability measure $\mu$, an estimate from below for the Kolmogorov--Sinai entropy of $T$ with respect to $\mu$ is suggested in terms of the entropies of $T$ with respect to $\mu_1$, $\mu_2$, \dots. 
B. Gurevich
math.DS