sentences:  Let "G" be a topological group and let "U" be a strongly continuous unitary representation of "G" in a separable Hilbert space "H".Denote by g the family of all one-parameter subgroups of "G".For each "δ" = { "δ"("t") | "t" ∈ R } ∈ g, let "U"("δ") denote the self-adjoint generator of the unitary one-parameter subgroup { "U"("δ"("t")) | "t" ∈ R }.