Aisagaliev S, Zhunussova Z, Akca H. Immersion principle for a variation calculus problem with boundary conditions. Int. j. math. phys. [Internet]. 2018 Dec. 29 [cited 2024 May 4];9(2):13-20. Available from: https://ijmph.kaznu.kz/index.php/kaznu/article/view/260