Perhaps you should try some spelling variations:
introduction interaction » introduction international, introduction introduction, interaction interaction
introduction abstraction » introduction absorption, introduction abstract, introduction abstracts
methods recursion » methods recursive, methods decision, method recursive
recursion array » recursion arrays
array formulas » area formulas, harrop formulas, array format

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((introduction interaction) or (introduction abstraction)) methods recursion array formulas~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((introduction interaction) OR (introduction abstraction)) methods recursion array formulas.
• Adding a wildcard symbol may retrieve word variants: ((introduction interaction) or (introduction abstraction)) methods recursion array formulas*.