Becker, E. Mediæval Visions of Heaven and Hell. John Murphy Company, Baltimore, 1899.
Langlois, E. Origines et sources du Roman de la Rose, chap. v. Paris, 1890.
For information regarding the dream motif in mediæval poems, see
Owen, D. Piers Plowman, A Comparison with some Earlier and Contemporary French Allegories, pp. 134-167. Hodder and Stoughton, London, 1912.
Neilson, W. A. The Origins and Sources of the Court of Love. (See "Dream-setting" in the index.) Ginn and Company, Boston, 1899.
Accounts of purgatory and of the terrestrial paradise will be found in "The Catholic Encyclopaedia." Further details regarding the earthly paradise are in Genesis ii, 8-17; Ezekiel xxviii, 13; "Phœnix," in Cook and Tinker's "Old English Poetry"; "Mandeville's Travels," XXXIII, and in Milton's "Paradise Lost," IV. Two critical studies of importance are
Gould, S. B. Curious Myths of the Middle Ages. London, 1874.
Coli, E. Il Paradiso Terrestre. Florence, 1897