Expanded/Split Volume:

A bibliographic unit whose physical capacity increases to accommodate additional material, usually revisions and additions. The increased capacity is usually in the form of additional physical volumes (binders). If a unit that is expanded is also part of a numbered multipart item or monographic series for which numbering has already been assigned, the numbering is adjusted to reflect any expansion. The method of adjusting the numbering varies slightly among publishers. For example, a volume originally numbered "volume 2" of a set may, when later expanded into two volumes, then be numbered "volume 2" and "volume 2A" or "volume 2A" and "volume 2B.