Bulgarian Academy of Science;

Faculty for Organization and Informatics, Varazdin, Croatia;

Faculty of Economy and Business Administration, University of Craiova, Romania;

Department of Economics and

Administrative Sciences, Fatih University, Istanbul, Turkey;

Faculty of Economics and Management, University of Defence, Czech Republic;

Technological Educational Institute of Kavala, Drama, Greece;

Pedagogical institute of

the Southern Federal University,

Rostov-on-Don, Russia;