In December 2016, our esteemed colleague, dear friend, mentor and father, Professor Emeritus D.Sc. Miroljub Kljajić, suddenly passed away. This was shocking news for all who knew him as a man full of life, creativity, wisdom, humour, and kindness. Sometimes it felt he was greater than life itself.

Prof. Mirojub Kljajić was born on 4^th November, 1943 in a little village Vražogrnci in the south of Serbia, then Yugoslavia. His childhood was marked by extreme shortages in the post-war Yugoslavia. At the age of 15, dreaming of becoming a pilot and being an outstanding student, he enrolled in the military school, which was the only schooling his family could afford. His harsh childhood experiences marked him for life. He was hard-working, strict to himself and to his colleagues, and never gave up. His thirst for knowledge, especially for the natural and technical sciences, but also profound love for art, drove him to seek possibilities for further studying. After finishing military school, he got his first employment in the army. During that time, serving in different cities (Kraljevo, Belgrade, Split, and Pula), he finished classical gymnasium and enrolled as a part-time student at a remote unit of Visoka tehniška šola (Higher Technical School) of Maribor, in Pula. After graduation he enrolled as a full-time student at the Faculty of Electrical Engineering of the University of Ljubljana while still working at the military airport in Pula. In his final year of studies he was placed in Ljubljana, graduated and finally demobilized from the military. He started to work as a postgraduate researcher at the Jožef Stefan Institute in Ljubljana, Section for automatics, bio-cybernetics and robotics. He finished his master’s studies under the supervision of Prof. Dr. France Bremšak. In 1973, he obtained his PhD in the field of bio-cybernetics from the University of Ljubljana, Faculty of Electrical Engineering under the supervision of academician Prof. Dr. Lojze Vodovnik.

In 1976, he started to work half-time at the Faculty of Organizational Sciences and half-time at the Jožef Stefan Institute. Since 2000 he was fully engaged with the Faculty. For many years, he was a chair of the Laboratory for Cybernetics and Decision Support Systems, transferring ideas from the field of automation, cybernetics and robotics to the world of organizational sciences. With his kindness and pedagogical instinct, he attracted and encouraged many excellent young researchers. Besides mentoring many undergraduate and graduate students, he also supervised ten PhD students. His laboratory was always full of vibrant discussions, ideas, and hard work, sometimes, if needed long into the night.

During his long and fruitful research years he published over 100 original scientific papers, 29 in esteemed journals with impact factors. According to the Web of Science his work was cited more than 500 times. Prof. Kljajić’s research interests were very wide and reflected his beliefs that topics are interconnected as in a complex system which he understood at a top level yet with full attention to the fine details.

Prof. Miroljub Kljajić was recognized in renowned international scientific circles and he thus held special symposiums at various international conferences. His most prominent symposium, Simulation Based Decision Support, was held in Baden-Baden, Germany, for many years at the InterSymp conference organized by The International Institute for Advanced Studies in Systems Research and Cybernetics. Lately he was a member of the editorial team of the journal Organizacija and a co-founder and editor of the International Journal of Information Technologies and Systems Approach. His meticulous research eye was a reason for being a prominent reviewer in renowned international scientific journals and conferences.

Having an outstanding scientific background and being a social persona with an exceptional ability to connect people with different backgrounds, he was a founder and for a longtime head of the research group “Decision Support Systems in Electronic Business” at the Faculty of Organizational Sciences, University of Maribor. This research group offered supportive environment to an outstanding number of senior and junior researchers and PhD students from a wide area of system approach research, solving complex managerial decision problems in the environment of rapid technological developments and electronic interactions. The wide plethora of research streams brought together under one umbrella within this research group describes Miroljub Kljajić’s personality best.

His main research interest, Simulation Based Decision Support, refers to the research stream,originating from cybernetics where systems can be efficiently managed by information both feedback and feedforward. Therefore, organizational systems inherently being complex in their nature, comprising of people, processes and technology, are the focus of this thematic issue. Hence, it is not surprising that this area has attracted scholars from all over the globe and from various fields of research such as Mathematics, Organizational sciences, Computer Science, Information Systems, Operational Research, etc. Although the research topics presented in this issue are diverse, we believe that they are well-balanced and harmonized under a common denominator – the Systems Approach Methodology, which makes this issue innovative and unique.

Prof. Miroljub Kljajić has left behind a well-established flourishing research garden where his successors can further develop and build upon his noble ideas. We believe that this thematic issue of Organizacija issue is only the first step.