Good point. The rendering of "sufficient" probably uses the triple-ligature for "ffi", where all 3 characters are merged.

The author, Peter Cheeseman, is a reputable figure and a solid practitioner. I'm sure he's just as annoyed that, on the second page, his own name is misspelled as "Cheesemart" ;-).

People may recognize him as a co-creator of the AutoClass software for Bayesian clustering, which was very popular in the late 1990s - the explanatory paper has 1700 citations.