Gurgul, Henryk, and Robert Syrek. “Mutual Information Between the Main Foreign Subindices: The Application of Copula Entropy Around WHO’s Declaration Date at the Time of the COVID-19 Pandemic”. International Entrepreneurship Review, vol. 10, no. 2, June 2024, pp. 7-24, https://doi.org/10.15678/IER.2024.1002.01.