[en] Explicit expressions were derived for the excitation strength functions of giant multipole resonances (GMR). The obtained formulae may be used to study the influence of anharmonic effects on the structure of GMR. The method of stength functions has essentially been used. Within the quasiparticle-phonon model a mathematical apparatus is constructed for calculating the strength functions of reduced multipole transition probabilities without solving the eigenvalue equations in doubly even deformed nuclei. It is shown that if the quasiparticle-phonon interaction is excluded, the model becomes harmonic