United States. Bureau of Economic Analysis
, Water Resources Council (U.S.)
and United States. Department of Agriculture. "Water Resources Regions, 1-8, Volume 3" in 1972 OBERS Projections : Regional Economic Activity in the United States; By Economic Area, Water Resources Region and Subarea, State, Historical and Projected, 1929-2020
(September 1972).
https://fraser.stlouisfed.org/title/9321/item/682137, accessed on January 20, 2026.