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          | Contents |  
          | We consider   waves, which obey the semilinear Klein-Gordon equation, propagating in the Friedmann-Lemaitre-Roberson-Walker spacetimes. The equations   in the de Sitter and  Einstein-de Sitter spacetimes  are the important particular cases.  We show the global in time existence   n the energy class of solutions of the Cauchy problem. |  |