The main area of my research is in the field of polynomial automorphisms, where I have investigated various phenomena related to the automorphisms of polynomial rings.  A major unsolved problem in this area is the famed Jacobian Conjecture, which has been the subject of many of my publications.  My work has focused on undertanding the problem through the lens of combinatorics and formal inverse.  In retirement I am still hard at work on this enigmatic problem.