In SOLO, you could use the subject search string below to pick up the most relevant books and ebooks (a few examples below)
United Nations. General Assembly. Declaration on the Rights of Indigenous Peoples
The Bodleian Library has been a depository library for United Nations material since 1950. The extensive collection of documents, official records and publications goes back to 1946. The collection is kept on open shelf in the Official Papers reading room located on floor 0 (Ground floor) of the Bodleian Law Library. The guide below well help you discover what is there, and what is available online.
Below are a couple of examples of titles available in the Official Papers collection