  In this paper we discuss various refinements and generalizations of a theorem
of Sankar Dutta and Paul Roberts. Their theorem gives a criterion for $d$
elements in a $d$-dimensional Noetherian Cohen-Macaulay local ring to be a
system of parameters, i.e., to have height $d$. We chiefly remove the
assumption that the ring be Cohen-Macaulay and discuss similar theorems.
