William Woo Seymour, The Cross in Tradition, History and Art, 1898, s. 356.
Edward Hawkins, The silver coins of England (1841), plate 1 (facing p. 8), no. 12: pre-Roman British coin: a cross with the four letters C, R, A, B placed in the four quadrants;
plate 3 (facing p. 16), no. 36: early Saxon sceat: diagonal cross with four dots in the four quadrants, no. 47: cross crosslet superimposed on a diagonal cross;
plate 4 (facing p. 18);
plate 5 (facing p. 22) no. 66: penny of Offa of Mercia: cross with four dots in the four quadrants (etc.)