Abstract
The review of the results of solvability research of multifrequency differential systems with
linearly transformed arguments and multipoint and integral conditions is shown in this paper. The
oscillation resonance condition, which depends on delay in fast variables, is introduced. The question of
existence and uniqueness of the solution is considered, and the justification of averaging method on fast
variables is investigated. The finest estimates of averaging method, which obviously depend on small
parameter, are obtained.

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