  We consider the quasi-two-dimensional pseudo-spin-1/2 Kitaev - Heisenberg
model proposed for A2IrO3 (A=Li, Na) compounds. The spin-wave excitation
spectrum, the sublattice magnetization, and the transition temperatures are
calculated in the random phase approximation (RPA) for four different ordered
phases, observed in the parameter space of the model: antiferomagnetic, stripe,
ferromagnetic, and zigzag phases. The N\'{e}el temperature and temperature
dependence of the sublattice magnetization are compared with the experimental
data on Na2IrO3.
