https://worldpopulationreview.com/world-city-rankings/largest-metro-areas-in-the-world
https://www.nationsonline.org/oneworld/bigcities.htm
https://www.sciencefocus.com/planet-earth/in-pictures-the-largest-cities-in-the-world
https://www.statista.com/statistics/912263/population-of-urban-agglomerations-worldwide/
https://zenodo.org/records/10458207
