The double spectral representation for the Feynman amplitude corresponding to a fourth-order diagram is proved and the spectral function is explicitly calculated. The conditions for the validity of such representation in the fourth order are obtained.
Citation Example:VIadimirov V. S. On the Double Spectral Representation of the Fourth-
order Feynman Amplitude // Ukr. Mat. Zh. - 1960. - 12, № 2. - pp. 132-146.