  Classical plasma with arbitrary degree of degeneration of electronic gas is
considered. In plasma N (N>2) collinear electromagnatic waves are propagated.
It is required to find the response of plasma to these waves. Distribution
function in square-law approximation on quantities of two small parameters from
Vlasov equation is received. The formula for electric current calculation is
deduced. It is demonstrated that the nonlinearity account leads to occurrence
of the longitudinal electric current directed along a wave vector. This
longitudinal current is orthogonal to the known transversal current received at
the linear analysis. The case of small values of wave number is considered.
