They are engraved in the work cited above, Le Tre Porte, seconda Porta, Tavole i. ii.
The bas-reliefs of S. Petronio were executed between 1425 and 1435. Those of the font in the chapel of S. John (not the lower church of S. John), at Siena, are ascribed to Quercia, and are in his manner; but when they were finished I do not know. They set forth six subjects from the story of Adam and Eve, with a compartment devoted to Hercules killing the Centaur Nessus, and another to Samson or Hercules and the Lion. The choice of subjects, affording scope for treatment of the nude, is characteristic; so is the energy of handling, though rude in detail. It may be worth while to notice here a similar series of reliefs upon the façade of the Colleoni Chapel at Bergamo, representing scenes from the story of Adam in conjunction with the labours of Hercules.
Ruskin's Modern Painters, vol. ii. chap, vii., Repose.
See Flaxman's Lectures on Sculpture, p. 310.