TIEES 2021: Trends and Innovations in E-Business, Education and Security Ninth International Scientific Web-conference of Scientists and PhD. Students or Candidates - Schmidt, Peter, 1968-; Rajnai, Zoltán; Jurík, Pavol, 1987-; Ancza, Erzsébet; Cárachová, Magdaléna (The Slovak Society for Economic Informatics, 2021)