Cioruța, B.-V., M. Coman, and A. L. Pop. “Enhancing and Conservation of Ecosystem through Philatelic Education in Europe: Think Green Concept (IV) - The Second Research Study on First-Day Covers”. Asian Journal of Advanced Research and Reports, Vol. 12, no. 1, July 2020, pp. 22-43, doi:10.9734/ajarr/2020/v12i130279.