They might've been worried about infringing copyright on de Villa Dei, <i>Carmen de Algorismo</i> (ca.XII)?<p>> <i>0 9 8 7 6 5 4 3 2 1</i><p><a href="https://gallica.bnf.fr/ark:/12148/btv1b84900936/f151.item" rel="nofollow">https://gallica.bnf.fr/ark:/12148/btv1b84900936/f151.item</a><p>see also <a href="https://inria.hal.science/hal-01615308/document" rel="nofollow">https://inria.hal.science/hal-01615308/document</a>