Compare, in the original texts collected by Pagi (tom. iii. A.D. 812, No. 7, A.D. 824, No. 10, etc.), the contrast of Charlemagne and his son: to the former the ambassadors of Michael (who were indeed disavowed)
more suo, id est lingua Graeca laudes dixerunt, imperatorem eum et appellantes;
to the latter,
Vocato imperatori Francorum, etc.