Reference for Keritot 24:43

העלמות מחולקין:

Thus even though the time that elapsed between the beginning and the end of the meal was longer than is required for the eating of a peras, yet since it was one protracted meal, he is liable; while the Rabbis retorted: If no more time has elapsed than is required for the eating of a peras, he is guilty, if more he is exempted?

Jastrow

Jastrow