Perhaps you should try some spelling variations:
"viral shedding problem" » "viral scheduling problem" (Expand Search), "viral scheduling problems" (Expand Search), "virus shedding problem" (Expand Search)
"coronal heating problem" » "coronal teaching problem" (Expand Search), "coronal routing problem" (Expand Search), "coronal making problem" (Expand Search)
"coronal setting problem" » "coronal routing problem" (Expand Search), "coronal routing problems" (Expand Search), "coronal solving problems" (Expand Search)

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("coronal heating problem") OR ((("viral shedding problem") OR ("coronal setting problem"))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"coronal heating problem\") OR (((\"viral shedding problem\") OR (\"coronal setting problem\"))))*".
• Removing quotes may allow a broader search: (( coronal heating problem ) OR ((( viral shedding problem ) OR ( coronal setting problem ))))*.