متى تم اكتشاف البكاء. في اي سنه تم استكشاف البكاء

Boisbaudran, Bunsen, Crookes, Kirchhoff, and others "hunting signatures"	, Federal Government of Canada
	Senese, Fred September 9, 2009

1983 , "Zinc production in medieval India", World Archaeology 15 2 , Industrial Archaeology, p.