Perhaps you should try some spelling variations:
"concerns criteria" » "cancer criteria", "concept criteria", "contests criteria"
"weil's criterion" » "kelly's criterion", "white's criterion", "levy's criterion"
"pde's criteria" » "ideas criteria", "peers criteria", "models criteria"
"weyl's criterion" » "well's criterion"

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: (((("weyl's criterion") OR ("weil's criterion"))) OR ((("pde's criteria") OR ("concerns criteria")))).
• Removing quotes may allow a broader search: (((( weyl's criterion ) or ( weil's criterion ))) or ((( pde's criteria ) or ( concerns criteria )))).
• Adding a wildcard symbol may retrieve word variants: (((("weyl's criterion") or ("weil's criterion"))) or ((("pde's criteria") or ("concerns criteria"))))*.