Source Data Reference for:

City = Riga
Time = 1850

City	Year	Size	Size Comment	Year Comment	Author	Title	Location
Riga	1850	70,000			Paul Bairoch	La population des villes europeennes de 800 a 1850
Riga	1850	61,000			Tertius Chandler	Four thousand years of urban growth	p24
Riga	1866	100,000	passed for the 1st time		Tertius Chandler	Four thousand years of urban growth	p542