Perhaps you should try some spelling variations:
linkage groups » linkage group
life groups » lie groups, like groups, line groups
link groups » sink groups, risk groups, disk groups
life group » lie group, line group, little group

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: (( ((life groups) OR (life group)) ) OR ((( linkage groups ) OR ( link groups )))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( ((life groups) OR (life group)) ) or ((( linkage groups ) or ( link groups ))))".
• Adding a wildcard symbol may retrieve word variants: (( ((life groups) OR (life group)) ) or ((( linkage groups ) or ( link groups ))))*.