Perhaps you should try some spelling variations:
"complicated diseases" » "complicated cases", "complex diseases", "mediated diseases"
"communicated disease" » "communicable disease", "communicate state", "communicated vision"
"related disease" » "related diseases"
"communicable diseases" » "communicate diseases"

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: (((("communicable diseases") OR ((("complicated diseases") OR ("related disease"))))) OR ("communicated disease")).
• Removing quotes may allow a broader search: (((( communicable diseases ) or ((( complicated diseases ) or ( related disease ))))) or ( communicated disease )).
• Adding a wildcard symbol may retrieve word variants: (((("communicable diseases") or ((("complicated diseases") or ("related disease"))))) or ("communicated disease"))*.