  In a recent paper [16], the authors proposed a BGK model for relativistic gas
mixtures based on the Marle-type approximation, which satisfies the fundamental
kinetic properties: non-negativity of distribution functions, conservation
laws, H-theorem, and indifferentiability principle. In this paper, we are
concerned with the stationary problems to the relativistic BGK model for gas
mixtures in slab geometry. We establish the existence of a unique mild solution
with the fixed inflow boundary data when the collision frequencies for each
species are sufficiently small.
