  Recent data of reactor neutrino experiments set more stringent constraint on
leptonic mixing patterns. We examine all possible patterns on the basis of
combinations of elementary correlations of elements of leptonic mixing matrix.
we obtain 62 viable mixing patters at 3$\sigma$ level of mixing parameters.
Most of these patterns can be paired via the {\mu}- interchange which changes
the octant of $\theta_{23}$ and the sign of $\cos{\delta}$. All viable patterns
can be classified into two groups: the perturbative patterns and
non-perturbative patterns. The former can be obtained from perturbing TBM. The
latter cannot be obtained from perturbing any mixing pattern whose
$\theta_{13}$ is zero. Different predictions of Dirac CP phase $\delta$ of
these two types of mixing patterns are discussed. Evolutions of mass matrices
of neutrinos with small mixing parameters are discussed via special mixing
patterns on the basis of flavor groups. In general cases, a small variation of
$\sin\theta_{13}$ may bring about large modifications to alignment of vacuum
expectation values in a mixing model. Therefore, small but nonzero
$\sin\theta_{13}$ brings a severer challenge to leptonic mixing models on the
basis of flavor groups than usual views.
