Source Data Reference for:

City = Ypres
Time = 1200

City	Year	Size	Size Comment	Year Comment	Author	Title	Location
Ieper	1200	40,000			Paul Bairoch	La population des villes europeennes de 800 a 1850
Ypres	1200	17,500	"btw 20,000 & 15,000"		Tertius Chandler	Four thousand years of urban growth	p16