Bruun, Johan Adolf: An enquiry into the art of the illuminated manuscripts of the Middle Ages. 1, Celtic illuminated manuscripts
https://download.digitale-sammlungen.de/pdf/17426515548888bsb10348117.pdf
https://www.digitale-sammlungen.de/en/view/bsb11795055?q=%28illuminated+manuscripts+The+Battle+of+Aljubarrota%29&page=119
