http://digitalcollections.stlawu.edu/collections/adirondack-sutra
From "The World Beyond," http://www.hrc.utexas.edu/educator/modules/gutenberg/books/world/
http://www.hrc.utexas.edu/educator/modules/gutenberg/books/before/
From "Illustrations from Early Printed Editions of the Commedia," https://digitaldante.columbia.edu/image/digitized-images/
From "Adapting Technology," hrc.utexas.edu/educator/modules/gutenberg/invention/adapting/