This contains a fork of Edward Tufte's ET Book (free Bembo) font. The originals may be found here: https://edwardtufte.github.io/et-book/ The originals have ligatures but don't contain any liga gsub table, so the ligatures don't get automatically inserted as they should. I used Fontforge to add an appropriate liga gsub table. You will notice there is no ff ligature (just fi, ffi, fl, and ffl). That's the way the font came, and I didn't add one. It doesn't seem to need one that badly; two adjacent f's dont run into each other like fi and fl did. Tufte's original fonts are .ttf files; mine are .otf files. This should not matter much; nearly every system supports OTF's. The .sfd files are the Fontforge projects for each font. If you don't care about editing fonts with Fontforge, you can just ignore them.