Perhaps you should try some spelling variations:
"ground theory" » "group theory", "grand theory", "growth theory"
"groups theory" » "group theory", "groups other"
"sound theory" » "bond theory", "und theory", "bound theorem"
"grounded 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 ((((("ground theory") OR ("sound theory"))) OR ("groups theory")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"grounded theory\") or (((((\"ground theory\") OR (\"sound theory\"))) or (\"groups theory\"))))".
• Removing quotes may allow a broader search: (( grounded theory ) or ((((( ground theory ) OR ( sound theory ))) or ( groups theory )))).
• Adding a wildcard symbol may retrieve word variants: (("grounded theory") or ((((("ground theory") OR ("sound theory"))) or ("groups theory"))))*.