C. H. Dakers, “Notes on Scottish Coins: (1) Rex Scottorum Pennies of David II.; (2) Edinburgh Light Groats of Robert III.; (3) Some James II. Groats of the Third Variety of the Fleur-de-lis Groats; and (4) Gilbert Kirkwood’s Mark on a Gold Coin of James V”, PSAS, vol. 72, pp. 122–128, Nov. 1938.