Determination of the structure of the spectrum of regular boundary value problems for differential equations by V.A. Il'in's method of anti-a priori estimates

Researchers used V.A II' in's method of anti-a priori estimates, to show that the spectrum of differential operators generated by regular boundary conditions, is empty or infinite. The method was also used to determine the structure of the spectrum of regular boundary value problems for differential equations. A theorem was formulated that used the result of the method that were formulated by the researchers, to meet their specific requirements.