Perhaps you should try some spelling variations:
"retarded treatment" » "retardant treatment", "related treatment", "retardant treatments"
"reported treatment" » "repeated treatment", "report treatment", "repeated treatments"
"headed treatment" » "blended treatment", "delayed treatment", "related treatment"

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: (("headed treatment") OR ((("retarded treatment") OR ("reported treatment")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"headed treatment\") or (((\"retarded treatment\") OR (\"reported treatment\"))))".
• Removing quotes may allow a broader search: (( headed treatment ) or ((( retarded treatment ) OR ( reported treatment )))).
• Adding a wildcard symbol may retrieve word variants: (("headed treatment") or ((("retarded treatment") OR ("reported treatment"))))*.