Source Data Reference for:

City = Leiden
Time = 1800

City	Year	Size	Size Comment	Year Comment	Author	Title	Location
Leiden	1800	31,000			Jan De Vries	European urbanization 1500-1800	p271
Leiden	1800	31,000			Tertius Chandler	Four thousand years of urban growth	p487
Leiden	1800	31,000			Tertius Chandler	Four thousand years of urban growth	p23
Leiden	1800	31,000			Paul Bairoch	La population des villes europeennes de 800 a 1850