From this letter I can understand that texts number 6 and 7 are missing in the manuscript of the third canto which you have in Boston. The original manuscript is in New York, and when I go there, maybe in April, I will find this for you: Revision history
Diff selection: Mark the radio buttons of the revisions to compare and hit enter or the button at the bottom.
Legend: (cur) = difference with latest revision, (prev) = difference with preceding revision, m = minor edit.