Canonical structural spine
The work's own structure
Reviewed edition: Claudius Ptolemaeus. Claudii Ptolemaei Opera quae exstant omnia, Volume 1, Parts 1-2. J. L. Heiberg, editor. Leipzig: Teubner, 1898-1903. Division axes: book → section. Structural nodes alone do not assert commentary citations.
Record-local commentary evidence
Commentary citations: work locus ↔ Dante locus
These citations occur in later commentary. They do not, by themselves, mean Dante cited this work.