On the existence of degenerate hypersurfaces in Sasakian manifolds (Q1296444)

In [Int. J. Math. Math. Sci. 16, 545-556 (1993; Zbl 0787.53048)] \textit{A. Bejancu} and \textit{K. L. Duggal} introduced indefinite Sasakian structures \((f,\xi,\eta,g)\) and constructed a special example of index \(s\) on \(\mathbb{R}^{2n+1}\). In the paper under review the author is concerned with hypersurfaces \(M\) of the latter space, which are tangent to the structure vector field \(\xi\). He shows: If \(s=n\) then \(M\) always is non-degenerate, but for \(s=1\) degenerate examples exist.