Perhaps you should try some spelling variations:
"theory and recursion library" » "theory and section library", "theory and recursion summary", "theory and recursion array"
"theory and equation library" » "theory and equations library", "theory and education library", "theory and emulation libbrary"

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

• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"theory and recursion library\") OR (\"theory and equation library\"))".
• Removing quotes may allow a broader search: (( theory and recursion library ) OR ( theory and equation library )).
• Adding a wildcard symbol may retrieve word variants: (("theory and recursion library") OR ("theory and equation library"))*.