Nilpotent Szabo, Osserman and Ivanov-Petrova pseudo-Riemannian manifolds
  We exhibit pseudo Riemannian manifolds which are Szab\'o nilpotent of arbitrary order, or which are Osserman nilpotent of arbitrary order, or which are Ivanov-Petrova nilpotent of order 3. 
B. Fiedler and P. Gilkey