Some properties of positive derivations on f-rings II

A counterexample is provided to show that Theorem 10(b)(i) in the article Some properties of positive derivations on f-rings by Henriksen and Smith is false. Correct proofs are given for some results in the paper that use Theorem 10(b)(i) in their proofs. Keywords: lattice-ordered ring, f-ring, positive derivation, polynomial ring.