Perhaps you should try some spelling variations:
assurance network » assurance author, assurance between, distance network
health assurance » health reassurance, health insurance, health assistance
health evidence » health science

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: (( health evidence ((network synthesis) OR (network systems)) report ) OR ( health assurance network synthesis report )).
• Adding a wildcard symbol may retrieve word variants: (( health evidence ((network synthesis) or (network systems)) report ) or ( health assurance network synthesis report ))*.