The collation of all known variants of a text is referred to as a variorum, namely a work of textual criticism whereby all variations and emendations are set side by side so that a reader can track how textual decisions have been made in the preparation of a text for publication. The Bible and the works of William Shakespeare have often been the subjects of variorum editions, although the same techniques have been applied with less frequency to many other works, such as Walt Whitman's Leaves of Grass, and the prose writings of Edward Fitzgerald.
Try to answer this question if possible (otherwise reply "unanswerable"): Name two works that are often the subject of a variorum.
The Bible and the works of William Shakespeare