of alternation depth 
can be evaluated over a complete lattice of height 
in time 
. The advantage of our proof is that it is both extremely short and extremely simple. Helmut Seidl. Fast and Simple Nested Fixpoints. Universität Trier, Mathematik/Informatik, Forschungsbericht, 96-05, 1996.
We give an alternative proof of the result of Long et al. in [12] that nested fixpoint expressions of alternation depth can be evaluated over a complete lattice of height in time . The advantage of our proof is that it is both extremely short and extremely simple.