  Spectrum of a first order sentence is the set of all $\alpha$ such that $G(n,
n^{-\alpha})$ does not obey zero-one law w.r.t. this sentence. We have proved
that the minimal number of quantifier alternations of a first order sentence
with an infinite spectrum equals 3. We have also proved that the spectrum of a
first order sentence with a quantifier depth 4 has no limit points except
possibly the points 1/2 and 3/5.
