Progress was made more recently by Howe,  Moy, Gopal Prasad and Bushnell and Kutzko, who developed a theory of types and classified the admissible dual (i.e.
Progress in this area was made more recently by Howe,  Moy, Gopal Prasad and Bushnell and Kutzko, who created a framework for categorizing and classifying duals.