Skender+kulenovic+ponornica+pdf+15 [ EXCLUSIVE ]

First, I need to figure out who Skender and Kulenovic are. The names sound like they might be authors or contributors to an academic paper. The term "Ponornica" is a bit tricky. Maybe it's a title or a concept they've researched? The "pdf 15" part suggests there's a PDF document available, possibly the 15th edition or a document with the number 15 in its title.