<gap> indicates a point where material has been omitted in a
transcription, whether for editorial reasons described in the TEI
header, as part of sampling practice, or because the material is
illegible, invisible, or inaudible. 3.4.3 Additions, Deletions, and Omissions
indicates approximately how much text has been omitted
from the transcription (using the unit specified on the
unit attribute), either because of editorial policy
or because a deletion, damage, or other cause has rendered
transcription impossible.