This article is only partially available online without a subscription to High Beam Research:
"The Survival of Humankind Is the Basic Humanist Value: An Interview with Svetozar Stojanović" by Paul Kurtz, Free Inquiry, Volume 16, Number 3, Summer, 1996.
This interview covers the history of the Praxis School as well as the later disintegration of Yugoslavia and Stojanović's political role during this period.
Presumably there is related material scattered in the archives of Free Inquiry; for example:
"A Serb's View of NATO's Bombs" by Svetozar Stojanovic, Volume 19, Number 3, Summer, 1999