On the elliptic Sturmian theory for general domains (Q1111755)

The well-known version of the Sturm-Picone comparison theorem by \textit{W. Leighton} [Proc. Am. Math. Soc. 13, 603--610 (1962; Zbl 0118.08202)] for ordinary, self-adjoint, second order differential equations is extended to self-adjoint elliptic differential equations. The basic domain \(G\) and the coefficients of the equation are not necessarily bounded, and no regularity hypotheses on the boundary \(G\) are required.