Díaz Díaz, Roberto Adolfo, Diana Carolina Verján Ávila, and José Alejandro Vera Calderón. “Analysis of International Trade of the Department of Tolima: Application of the Gravity Model in the Period 2009-2019”. In Challenges and Trends for the Sustainability of Organizations in Scenarios of Uncertainty, 224–247. Administrative, Accounting, Economic and Business. Colombia,CO: Sello Editorial UNAD, 2022. Accessed November 2, 2026. https://libros.unad.edu.co/index.php/selloeditorial/catalog/book/194/chapter/1376.