Available on open shelf in the Official Papers reading room.
International statistical yearbook O.LN per. 13 (1926-1941/42)
Monthly bulletin of statistics O.LN per. 10 (1921-1942)
Monthly summary O.LN per.8 (v.1:1920-v.8:1940)
Official Journal O.LN per.1 (v.1:1920-v.21(1940)
Also in full text via HeinOnline
Proceedings and resolutions of the Assembly were published in the Special Supplement of the Official Journal 1920-1938.
Minutes of the Council were published in the Journal 1922-1939
General texts about the League of Nations can be found on the open shelves in the Bodleian Law Library in the international section at Internat 685