1. Einstein, A. (1920). Relativity: The Special and General Theory (Translated by Robert W. Lawson). Henry Holt and Company. https://www.f.waseda.jp/sidoli/Einstein_Relativity.pdf
2. Flater, D. (2017). WXTide32 Is Based on the UNIX Program XTide Version 1.6.2. http://www.wxtide32.com/
3. Hossenfelder, S. (2017). Is Space-Time Fluid? Institute of Art and Ideas. https://iai.tv/articles/is-space-time-fluid-auid-897#:~:text=Physicists%20have%20gathered%20evidence%20that,%20the%20two%20were%20distant%20cousins
4. What is the principle of equivalence?