Formulas of repetition in Dante's Commedia

the long version

"Formulas are usually understood as rhetorical devices that are found in close textual proximity and, because they are intended for emphasis, cannot possibly escape the notice of the reader. The formulas Lloyd H. Howard traces in this study are far more difficult to find because they are hidden deep in the structure of the Commedia and at considerable distances from one another. For example Howard demonstrates that when the reader notes that the formula "ne l'etterno esilio" - in eternal exile - re-occurs in Purgatorio 21 accompanied by the same rhyme words as when it first appears in Inferno 23, it is a sign that these two episodes can be linked for further interpretation, despite the 32 cantos of intervening textual space."--BOOK JACKET.