In Chaucer’s Squier’s Tale, a sword of similar quality is
introduced: 
        And other folk have wondred on the sweard,
        That could so piercen through every thing;
        And fell in speech of Telephus the king,
        And of Achillcs for his queint spere,
        For he couth with it both heale and dere. 
So Shakspeare, Henry vi. p. ii. a. 5. s. 1. 
        Whose smile and frown like to Achilles’ spear
        Is able with the change to kill and cure.

v. 14.  Orlando.l
        When Charlemain with all his peerage fell
               At Fontarabia
               Milton, P. L. b. i. 586. 
See Warton’s Hist. of Eng.  Poetrg, v. i. sect. iii. p. 132.  “This is the horn which Orlando won from the giant Jatmund, and which as Turpin and the Islandic bards report, was endued with magical power, and might be heard at the distance of twenty miles.”  Charlemain and Orlando are introduced in the Paradise, Canto xviii.

v. 36.  Montereggnon.] A castle near Sienna.

v. 105.  The fortunate vale.] The country near Carthage.  See Liv.  Hist. l. xxx. and Lucan, Phars. l. iv. 590.  Dante has kept the latter of these writers in his eye throughout all this passage.

v. 123.  Alcides.] The combat between Hercules Antaeus is adduced by the Poet in his treatise “De Monarchia,” l. ii. as a proof of the judgment of God displayed in the duel, according to the singular superstition of those times.

v. 128.  The tower of Carisenda.] The leaning tower at Bologna

Canto xxxii.

v. 8.  A tongue not us’d
        To infant babbling.]
        Ne da lingua, che chiami mamma, o babbo. 
Dante in his treatise " De Vulg.  Eloq.” speaking of words not admissble in the loftier, or as he calls it, tragic style of poetry, says- “In quorum numero nec puerilia propter suam simplicitatem ut Mamma et Babbo,” l. ii. c. vii.

v. 29.  Tabernich or Pietrapana.] The one a mountain in Sclavonia, the other in that tract of country called the Garfagnana, not far from Lucca.

v. 33.  To where modest shame appears.] “As high as to the face.”

v. 35.  Moving their teeth in shrill note like the stork.]
        Mettendo i denti in nota di cicogna. 
So Boccaccio, G. viii. n. 7.  “Lo scolar cattivello quasi cicogna divenuto si forte batteva i denti.”

v. 53.  Who are these two.] Alessandro and Napoleone, sons of Alberto Alberti, who murdered each other.  They were proprietors of the valley of Falterona, where the Bisenzio has its source, a river that falls into the Arno about six miles from Florence.

v. 59.  Not him,] Mordrec, son of King Arthur.

v. 60.  Foccaccia.] Focaccia of Cancellieri, (the Pistoian family) whose atrocious act of revenge against his uncle is said to have given rise to the parties of the Bianchi and Neri, in the year 1300.  See G. Villani, Hist. l, viii. c. 37. and Macchiavelli, Hist. l. ii.  The account of the latter writer differs much from that given by Landino in his Commentary.