Perhaps you should try some spelling variations:
"ill-mixed problems" » "ill-wicked problems", "ill-based problems"
"ill-posed problem" » "ill-based problem"
"ill-posed problems" » "ill-based problems"
"ill-mixed problem" » "ill-based problem"

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: (((("ill-posed problem") OR ("ill-mixed problem"))) OR ((("ill-posed problems") OR ("ill-mixed problems")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"ill-posed problem\") OR (\"ill-mixed problem\"))) or (((\"ill-posed problems\") or (\"ill-mixed problems\"))))".
• Removing quotes may allow a broader search: (((( ill-posed problem ) OR ( ill-mixed problem ))) or ((( ill-posed problems ) or ( ill-mixed problems )))).
• Adding a wildcard symbol may retrieve word variants: (((("ill-posed problem") OR ("ill-mixed problem"))) or ((("ill-posed problems") or ("ill-mixed problems"))))*.