  The Neumann problem with a small parameter
$$(\dfrac{1}{\epsilon}L_0+L_1)u^\epsilon(x)=f(x) \text{for} x\in G,
.\dfrac{\partial u^\epsilon}{\partial \gamma^\epsilon}(x)|_{\partial G}=0$$ is
considered in this paper. The operators $L_0$ and $L_1$ are self-adjoint second
order operators. We assume that $L_0$ has a non-negative characteristic form
and $L_1$ is strictly elliptic. The reflection is with respect to inward
co-normal unit vector $\gamma^\epsilon(x)$. The behavior of
$\lim\limits_{\epsilon\downarrow 0}u^\epsilon(x)$ is effectively described via
the solution of an ordinary differential equation on a tree. We calculate the
differential operators inside the edges of this tree and the gluing condition
at the root. Our approach is based on an analysis of the corresponding
diffusion processes.
