Perhaps you should try some spelling variations:
productive learning » predictive learning, proactive learning, production learning
product learning » production learning, prompt learning, product licensing
product planning » project planning, production planning
project learning » project planning, project defining, project running

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: %((adult learning) OR (((((((product learning) OR (productive learning))) OR (product planning))) OR (project learning))))%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%((adult learning) or (((((((product learning) OR (productive learning))) or (product planning))) or (project learning))))%22".
• Adding a wildcard symbol may retrieve word variants: %((adult learning) or (((((((product learning) OR (productive learning))) or (product planning))) or (project learning))))%22*.