Bezkorovaina, L. L., & Vashpanova, T. Y. (2010). $A$-deformations of a surface with stationary lengths of $LGT$-lines. Ukrains’kyi Matematychnyi Zhurnal, 62(7), 878–884. https://umj.imath.kiev.ua/index.php/umj/article/view/2921