44 U.S.C. § 1912

Not more than two depository libraries in each State and the Commonwealth of Puerto Rico may be designated as regional depositories, and shall receive from the Superintendent of Documents copies of all new and revised Government publications authorized for distribution to depository libraries. Designation of regional depository libraries may be made by a Senator or the Resident Commissioner from Puerto Rico within the areas served by them, after approval by the head of the library authority of the State or the Commonwealth of Puerto Rico, as the case may be, who shall first ascertain from the head of the library to be so designated that the library will, in addition to fulfilling the requirements for depository libraries, retain at least one copy of all Government publications either in printed or microfacsimile form (except those authorized to be discarded by the Superintendent of Documents); and within the region served will provide interlibrary loan, reference service, and assistance for depository libraries in the disposal of unwanted Government publications. The agreement to function as a regional depository library shall be transmitted to the Superintendent of Documents by the Senator or the Resident Commissioner from Puerto Rico when the designation is made. The libraries designated as regional depositories may permit depository libraries, within the areas served by them, to dispose of Government publications which they have retained for five years after first offering them to other depository libraries within their area, then to other libraries.