1. Cooper BS, Worthington NL: National health expenditures, 1929–72. Social Security Bulletin, January 1973
2. Cooper BS, Worthington NL: Compendium of National Health Expenditures Data, Social Security Administration, DHEW Pub No (SSA) 73-11903
3. Cooper BS, Worthington NL: National health expenditures, calendar years 1929–71. Research and Statistics Note No. 3, March 6, 1973, Social Security Administration