Bulgarian Academy of Science;

Union of Scientists in Bulgaria;

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;

Department of Forestry and Natural Environment,

Department of Business Administration, School of Business and Economics, Technological Educational Institute of Kavala, Drama, Greece;

Pedagogical institute of the Southern Federal University,

Rostov-on-Don, Russia.