Cluster properties in relativistic quantum mechanics of N-particle   systems
  A general technique is presented for constructing a quantum theory of a finite number of interacting particles satisfying Poincar\'e invariance, cluster separability, and the spectral condition. Irreducible representations and Clebsch-Gordan coefficients of the Poincar\'e group are the central elements of the construction. A different realization of the dynamics is obtained for each basis of an irreducible representation of the Poincar\'e group. Unitary operators that relate the different realizations of the dynamis are constructed. This technique is distinguished from other solutions of this problem because it does not depend on the kinematic subgroups of Dirac's forms of dynamics. Special basis choices lead to kinematic subgroups. 
W. N. Polyzou (The University of Iowa)