Perhaps you should try some spelling variations:
interaction sources » interaction forces, interaction studies, interaction series
skills interaction » skill integration, skills instructions, skills introduction
essential skills » essential oils
hiv transmission » child transmission, _ transmission
lines » line

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( essential skills interaction sources ) or ( _ hiv transmission lines ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( essential skills interaction sources ) OR ( _ hiv transmission lines )).
• Adding a wildcard symbol may retrieve word variants: (( essential skills interaction sources ) or ( _ hiv transmission lines ))*.