1. Chandra, A., Kozen, D., Stockmeyer, L.: Alternation. Journal of the ACM, 28, 114-133, 1981.
2. Geffert, V.: A Communication Hierarchy of Parallel Computations. Theor. Comput. Sci., 198, No. 1-2, 99-130, 1998.
3. Hromkovič J., Karhumäki, J., Rovan, B., Slobodová, A.: On the power of synchroniza-tion in parallel computations. Discrete Appl. Math. 32, 155-182, (1991).
4. Valiant, L. G.: A Bridging Model for Parallel Computation, Comm. of the ACM, 33, No. 8,103-111, 1990.
5. Wiedermann, J.: On the Power of Synchronization. Elektronische Informationsverar-beitung und Kybernetik (EIK), 25, No. 10, 499-506, 1989.