[23] Hofenk De Graaff, Natural Dyestuffs, Origin, Chemical Composition 35-36; Ortega, Black Dyed Wool in North Western Europe, 166-171.
[23] Hofenk De Graaff, Natural Dyestuffs, Origin, Chemical Composition 35-36; Ortega, Black Dyed Wool in North Western Europe, 166-171.