VONGREJ, Marián. Arrow as a Symbol of (Social) Business Model - Introduction to the Area of Economics. In Sociaľna robota v Ukrajini: teorija i praktika : naukovo-metodičnij žurnal. - Kijiv : Vidavnictvo Aspekt-Poligraf, 2017. ISSN 2415-8011, 2017, no. 1-2, s. 111-115. VEGA 1/0367/17.