Perhaps you should try some spelling variations:
"complications disease" » "applications disease", "complications case", "replication disease"
"complicated diseases" » "complicated cases", "complex diseases", "mediated diseases"
"complicate disease" » "compleat disease", "communicated disease", "complicated case"

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 ((("communicable disease") OR ((((("complicate disease") OR ("complicated diseases"))) OR ("complications disease")))))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"communicable diseases\") or (((\"communicable disease\") or (((((\"complicate disease\") OR (\"complicated diseases\"))) or (\"complications disease\"))))))".
• Removing quotes may allow a broader search: (( communicable diseases ) or ((( communicable disease ) or ((((( complicate disease ) OR ( complicated diseases ))) or ( complications disease )))))).
• Adding a wildcard symbol may retrieve word variants: (("communicable diseases") or ((("communicable disease") or ((((("complicate disease") OR ("complicated diseases"))) or ("complications disease"))))))*.