The best place to begin a search for international statistical material. OECD environmental data. Biennial compilation of environmental statistics for OECD countries. Statistical abstract of the United States. The first place to go for almost all statistical questions domestic and international.
Tables provide useful citations into the literature.
Statistical reference index. Very useful for getting into state and commercial statistical sources. Index to hearings and reports coming out of Congress. Also available in print as CIS Index and covers 1970-present. Commercial index which covers both journal articles on public policy and government documents, especially hearings.