In spite of progress in solving some problems of classical plasma, there is not general theory to calculate its properties with taking in account collision processes. Frequently the diffusion approximation is used. In this way St(f)=-div(f), where divergence is defined in moment space. This approach is in pulse changing in result on collision is very small and transport crosssection is about 4пee'do/(m^2*v^4).
But the general approach of of physical kinetics remains in effect, and the equation as a df/dt=St(f) on a distribution functions of ions and electrons with Maxwell's equations well describes plasma physical properties