Perhaps you should try some spelling variations:
aggregation functional » aggregation functions, aggregation function, aggregate function
aggregate functional » aggregate function, aggregate fraction, aggregates national
aggregate functions » aggregation functions
functions income » functional income, functions come, functions inline

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• The words AND, OR and NOT may confuse the search; try adding quotes: "\"((\\"aggregate functions income distribution\\") or (\\"((aggregate functional) OR (aggregation functional)) income distribution\\"))*\"".
• Removing quotes may allow a broader search: (( aggregate functions income distribution ) or ( ((aggregate functional) OR (aggregation functional)) income distribution ))*.