Perhaps you should try some spelling variations:
presentation based » presentation ease, representations based, presentation layer
brief presentation » re presentation, budget presentation, self presentation
commercial actors » commercial crops, commercial sector, commercial farmers
commercial crisis » commercial crimes, commercial risks, commercial credits
sources brief » sources series, sources brfss
based studies » case studies

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((commercial actors) or (commercial crisis)) sources brief presentation based studies.~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((commercial actors) OR (commercial crisis)) sources brief presentation based studies..
• Adding a wildcard symbol may retrieve word variants: ((commercial actors) or (commercial crisis)) sources brief presentation based studies.*.