Perhaps you should try some spelling variations:
"math skills series." » "math skills surveys.", "math skills service.", "math skills studies.", "path skills series."
"mat skills series." » "mat skills surveys.", "mat skills service.", "mat skills studies.", "smart skills series.", "what skills series.", "want skills series."
"motor soil surveys." » "motor social surveys.", "motor school surveys.", "motor skills surveys.", "monitor soil surveys.", "motor skill surveys.", "poor soil surveys."

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

• Performing a fuzzy search may retrieve terms with similar spellings: (((("math skills series.") OR ("mat skills series."))) or ("motor soil surveys."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("math skills series.") OR ("mat skills series."))) OR ("motor soil surveys."))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"math skills series.\") OR (\"mat skills series.\"))) or (\"motor soil surveys.\"))*".
• Removing quotes may allow a broader search: (((( math skills series. ) OR ( mat skills series. ))) or ( motor soil surveys. ))*.