Grushka, Ya. I. “Self-Consistent Translational Motion of Reference Frames and Sign-Definiteness of Time in Universal Kinematics”. Methods of Functional Analysis and Topology 24, no. 2 (June 25, 2018): 107–119. Accessed December 15, 2025. https://zen.imath.kiev.ua/index.php/mfat/article/view/689.