Perhaps you should try some spelling variations:
"theory and emission linear" » "theory and emission line", "theory and emission lines", "theory and emission near"
"theory and vision library" » "theory and design library", "theory and gson library", "theory and visual library"
"theory and vision linear" » "theory and piston linear", "theory and von linear", "theory and motion linear"

Try widening your search to All Fields.

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (("theory and vision library") OR ((("theory and vision linear") OR ("theory and emission linear")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"theory and vision library\") or (((\"theory and vision linear\") OR (\"theory and emission linear\"))))".
• Removing quotes may allow a broader search: (( theory and vision library ) or ((( theory and vision linear ) OR ( theory and emission linear )))).
• Adding a wildcard symbol may retrieve word variants: (("theory and vision library") or ((("theory and vision linear") OR ("theory and emission linear"))))*.