  The electronic states in the monolayer graphene with the short-range
perturbation asymmetric with respect to the band index are analized. The study
was made for the separable in the angular momentum representation potential
basing on the (2+1)-dimensional Dirac equation. The characteristic equation for
bound and resonance states obtained in the present paper is compared with one
derived earlier for the same problem with different approach. The momentum
representation approach used in the present paper allowed us to obtain the
satisfactory regularization of the Hadamar incorrect boundary problem stemming
from the potential singularity.
