Lukovsky, I. O., Mykhailyuk, O. V., & Timokha, A. N. (1996). On one variational criterion of stability of pseudoequilibrium forms. Ukrains’kyi Matematychnyi Zhurnal, 48(11), 1494-1500. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/5203