  New observables for searching for Z' virtual states in processes
e^+e^-\to\bar{f}f are proposed. They are based on the relations following due
to renormalizability of an underlying theory between the parameters of the
low-energy effective Lagrangian. Two types of the Z' interactions are
considered. The observables allow to pick up uniquely the signals of both Z'
bosons. The search for the Z' at future linear colliders and the treating of
the LEP data are discussed.
