Remarks on a new inverse nodal problem

In a recent paper, X. F. Yang proved a uniqueness theorem on inverse nodal problems that links to inverse spectral theory, on one hand, and reduces th e redundancy of the classical inverse nodal problems, on the other hand. In this note we improve Yang's theorem by weakening its conditions and simpli fying its proof. We also discuss variants of Yang's theorem. (C) 2000 Acade mic Press.