Yalom 's approach to group therapy has been very influential not only in the USA but across the world .
After World War II , group psychotherapy was further developed by Moreno , Samuel Slavson , Hyman Spotnitz , Irvin Yalom , and Lou Ormont .
Irvin Yalom 's approach to group therapy has been very influential not only in the USA but across the world .
After World War II , group psychotherapy was further developed by Moreno , Samuel Slavson , Hyman Spotnitz , Irvin Yalom , and Lou Ormont .