Before revision:  In particular, low-complexity replication policies are designed , and are rigorously proven to be delay-optimal or near delay-optimal among all non-preemptive and causal policies.
After revision:  In particular, low-complexity replication policies are designed , and are rigorously proven to be delay-optimal or near delay-optimal in stochastic ordering among all causal and non-preemptive and causal policies.