The first job of all editors is to gather relevant variant forms of the work to be edited and, by collation, establish the relationship they bear to one another. […] Scholars engaged in critical editing must do character-for-character comparison of all versions that could conceivably have been authoritatively revised or corrected. Collation forms the groundwork needed to determine, first, what changes occurred during composition of the work or between the time the work left the author‘s hand and the time it last rolled off the press while the author was living and, second, to determine whether the author, or an editor or compositor, was responsible for those changes.