"The Austrian imperial standard has, on a yellow ground, the black double-headed eagle, on the breast and wings of which are imposed shields bearing the arms of the provinces of the empire. The flag is bordered all round, the border being composed of equal-sided triangles with their apices alternately inwards and outwards, those with their apices pointing inwards being alternately yellow and white, the others alternately scarlet and black." (Chisholm 1911, p. 461)
"The imperial banner was a golden yellow cloth...bearing a black eagle...The double-headed eagle was finally established by Sigismund as regent..." (Smith 1975, pp. 114–119)