Perhaps you should try some spelling variations:
learning contents » learning contexts, learning content, learning concepts
contents series » movements series
term learning » team learning, firm learning, reform learning
form learning » firm learning, formal learning, forman learning
center series » century series, gender series, center studies

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (( a learning contents series. ) or ( ((term learning) or (form learning)) center series. ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( a learning contents series. ) OR ( ((term learning) OR (form learning)) center series. )).
• Adding a wildcard symbol may retrieve word variants: (( a learning contents series. ) or ( ((term learning) or (form learning)) center series. ))*.