Perhaps you should try some spelling variations:
"processing sampling statistics methods." » "processing spain statistics methods.", "processing sampling statistical methods.", "processing sampling statistics methodology."
"processing units statistics methods." » "processing units statistical methods.", "processing units statistics methodology.", "processing data statistics methods.", "processing zones statistics methods.", "processing users statistics methods.", "processing states statistics methods.", "processing chile statistics methods."

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("processing units statistics methods.") or ("processing sampling statistics methods."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("processing units statistics methods.") OR ("processing sampling statistics methods."))*.
• Removing quotes may allow a broader search: (( processing units statistics methods. ) or ( processing sampling statistics methods. ))*.