Two-dimensional zero-gap electronic states at a magnetic field

This work was firstly published in 1986 \cite{we}. No real two-dimensional object with the zero-gap quasi-relativistic spectrum was known in that time. Such an object is well known now: this is graphene. That is why we decided to present it again as a e-print in a slightly modified form. A density of the two-dimensional zero-gap electronic states at the quantizing magnetic field in the presence the Gaussian random potential has been calculated. The problem is reduced to zero-dimensional spinor field theory using the holomorphic supersymmetric representation. The calculated density of states in the case of the mass perturbation has a delta function peak in the Dirac point.This peak smears due to the potential perturbation.