Clarke, Francis. “Continuity of Solutions to a Basic Problem in the Calculus of Variations”. ANNALI SCUOLA NORMALE SUPERIORE - CLASSE DI SCIENZE 4, no. 3 (December 4, 2009): 511-530. Accessed June 19, 2025. http://20.103.181.36/index.php/annaliscienze/article/view/77.