Perhaps you should try some spelling variations:
"experimental progress" » "experimental program", "experimental problems", "experimental stress"
"experimental forest" » "experimental test", "experimental stress", "experimental tests"
"experimental facts" » "experimental aspects", "experimental facilities", "experimental fluid"

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: (("experimental facts") OR ((("experimental forest") OR ("experimental progress"))))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"experimental facts\") or (((\"experimental forest\") OR (\"experimental progress\"))))*".
• Removing quotes may allow a broader search: (( experimental facts ) or ((( experimental forest ) OR ( experimental progress ))))*.