Perhaps you should try some spelling variations:
"Made simple learning" » "Made improve learning"
"made ensemble learning" » "image ensemble learning", "maps ensemble learning", "face ensemble learning"
made complex » mad2 complex, grade complex, made compleat

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: (((("Made simple learning") OR ("Made complex learning"))) OR ("made ensemble learning")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"Made simple learning\") OR (\"Made complex learning\"))) or (\"made ensemble learning\"))".
• Removing quotes may allow a broader search: (((( Made simple learning ) OR ( Made complex learning ))) or ( made ensemble learning )).
• Adding a wildcard symbol may retrieve word variants: (((("Made simple learning") OR ("Made complex learning"))) or ("made ensemble learning"))*.