A complete sheep set from the 15th Congress to the close of the 53d Congress numbers slightly over 3343V., and will require 860 feet of shelving, or six modern iron book stacks.
Though it is done in a few cases, the subject classification of the sheep set is not to be recommended.

Where subject classification, or the incorporation of the documents in the general library, is desired, the cloth set is preferable, and is in most cases procurable.

If a library can afford shelf room for both, it will be found more satisfactory to keep the sheep set intact, and to make a selection of such reports from the cloth set as will be locally useful to the library.
No small library should undertake to acquire any documents but those for which it has an actual use; only the largest libraries can afford the task of filling up sets of documents simply for the sake of having a complete record.
Small libraries, and all libraries in need of any special report or document, can get it, in most cases, by applying to the superintendent of documents.

Return all your duplicates to the superintendent of documents; arrangements for their transportation will be made by him upon notification, and anything he has that is needed will be sent in exchange.
Do not try to collect a complete set of government documents; the government of the United States has not yet been able to do that..