form L= ∂/∂ t+(x^ na (x)+ ix^ mb (x)) ∂/∂ x, b\not\equiv0 and a (0)≠ 0, defined on\Omega_
ϵ=(-ϵ, ϵ) * S^ 1, ϵ> 0, where a and b are real-valued smooth functions in (-ϵ, ϵ) and m≥ 2
n. It is shown that given f belonging to a subspace of finite codimension of C^ ∞ (\Omega_
ϵ) there is a solution u ∈ L^ ∞ of the equation Lu= f in a neighborhood of Σ; moreover, the
L∞ regularity is sharp.