Perhaps you should try some spelling variations:
collaborative series » collaborative services, collaborative studies, collaborative agencies
collaborative roles » collaborative process, collaborative problem, collaborative forest
wetlands digital » sweetland digital, methods digital, stand digital
digital terrain » digital teaching, digital theorien

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

• Performing a fuzzy search may retrieve terms with similar spellings: wetlands digital terrain ((collaborative series) or (collaborative roles))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: wetlands digital terrain ((collaborative series) OR (collaborative roles)).
• Adding a wildcard symbol may retrieve word variants: wetlands digital terrain ((collaborative series) or (collaborative roles))*.