As you might have already guessed, "Inferno" is just a part of the work of this classical author. So the part mentioned above (Inferno) happens to be the first of three existing ones as the poem describes three other sides: Inferno, Purgatorio, Paradiso.

It's also an interesting fact that the original title of the work was just "Comedy" - the "Divine" attachment appeared more than 200 years after the poem had been written.

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