Ćwiąkała-Małys, Anna, and Iwona Piotrowska. “The Problem of the Grey Area in E-Trade in Poland”. Regional Barometer. Analyses & Prognoses 15, no. 3 (January 12, 2018): 41–49. Accessed July 11, 2025. https://czaz.akademiazamojska.edu.pl/index.php/br/article/view/423.