  It is widely believed that Rasba spin splitting occurs only in systems
lacking space inversion invariance. In this letter we present analytical
analysis which suggests that non-zero Rashba spin splitting occurs in systems
possessing space inversion invariance. We present numerical simulations which
confirm that non-zero Rashba spin splitting occurs in symmetric structures but
this splitting is several orders of magnitude smaller than the Rashba spin
splitting due to broken space inversion invariance.
