Database: world_development_indicators
Question: List the sources for the Net Migration in South American countries in 2002.
SQL: SELECT T2.Source FROM CountryNotes AS T1 INNER JOIN Series AS T2 ON T1.Seriescode = T2.SeriesCode INNER JOIN Country AS T3 ON T1.Countrycode = T3.CountryCode INNER JOIN SeriesNotes AS T4 ON T2.SeriesCode = T4.Seriescode WHERE T4.Year LIKE '%2002%' AND T2.IndicatorName = 'Net migration'