Popov, B. S. “UBER DIE INTEGRATION DER LINEAREN DIFFERENTIALGLEICHUNG DRITTER ORDNUNG IN GESCHLOSSENER FORM”. Matematichki Bilten 6, no. 1 (January 1, 1956). Accessed June 13, 2026. https://bilten.smm.org.mk/index.php/bilten/article/view/1207.