• Global Grey (English)
  https://www.globalgreyebooks.com/authors.html
• Motion Mountain (English)
  http://www.motionmountain.net
• The On-Line Books Page (English)
  http://digital.library.upenn.edu/books
• Perseus Digital Library (Many Languages)
  http://www.perseus.tufts.edu/hopper
• Retro-Bibliothek (German)
  http://www.retrobibliothek.de/retrobib/suche.html
• Shakespear's Complete Works (English)
  http://shakespeare.mit.edu/works.html