Perhaps you should try some spelling variations:
"extended theory" » "extended memory", "extension theory"
"blended theory" » "blending theory", "blended query", "blended shore"
"grounded theory" » "ground theory", "founded theory", "bounded theory"

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