The series comes from the 'Current Population Survey (Household Survey)'
The source code is: LNU03008876
Source: US. Bureau of Labor Statistics
Release: Employment Situation
US. Bureau of Labor Statistics, Number of Civilians Unemployed for 15 to 26 Weeks [LNU03008876], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/LNU03008876/, July 30, 2015.