REIFF, Marian - SURMANOVÁ, Kvetoslava - IVANIČOVÁ, Zlatica. Digital economy - cluster analysis of the use of information and communication technologies by the enterprises in the European union. In Competition. International scientific conference. Competition : proceedings of 9th annual international scientific conference : [18. 5. 2017, Jihlava, Česká Republika]. - Jihlava : Vysoká škola polytechnická, 2017. ISBN 978-80-88064-31-2, pp. 689-697 online. VEGA 1/0245/15, VEGA 1/0285/14.