Akiyama, K., Alberdi, A., Alef, W., and 266 more including, Azulay, R., Bach, U., et al. (2022). First Sagittarius A* Event Horizon Telescope Results. IV. Variability, Morphology, and Black Hole Mass. \apjl, 930(2): L15, pp. L15. doi:10.3847/2041-8213/ac6736.