Michelangelo Buonarroti – Studies for the Libyan Sibyl (recto); Studies for the Libyan Sibyl and a small Sketch for a Seated Figure (verso) – The Metropolitan Museum of Art https://www.metmuseum.org/art/collection/search/337497
annotated in pen and brown ink at upper right: 58 Annotated by early 16th century hand
to lie underneath the main study), while the highly rendered motifs of the left hand