Key points are not available for this paper at this time.
The article defines a class of regular first-order differential operators the main part of which contains the involution operator and nonconstant coefficient functions. A scheme for proving the unconditional basis property of the eigenfunctions and associated functions of regular differential operators of this type is provided under some additional conditions. Examples of operators for which root functions do not form a basis are constructed.
Granilshchikova et al. (Mon,) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: