Perhaps you should try some spelling variations:
comparison series » comparison studies, comparison string, comparison sites
compass varies » compass bearings
compass series » compact series, complex series, compass exercises

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: (( the ((((compass series) OR (compass varies))) OR (comparison series)) ) OR ( the complex queries )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( the ((((compass series) OR (compass varies))) or (comparison series)) ) or ( the complex queries ))".
• Adding a wildcard symbol may retrieve word variants: (( the ((((compass series) OR (compass varies))) or (comparison series)) ) or ( the complex queries ))*.