The Paston Letters, A.D. 1422-1509…
“ In this Index segment of the Paston Letters, unambiguous errors in punctuation and typography have been silently corrected or regularized. Other errors are marked with mouse-hover popups, and are listed again at the end of their entry. The word “invisible” means that there is an appropriately sized blank space, but the letter or punctuation mark itself is missing. ”
