Perhaps you should try some spelling variations:
"nonlinear potential theory" » "nonlinear material theory", "nonlinear properties theory"
"nonlinear spectral theorem" » "linear spectral theorem", "nonlinear structural theorem", "nonlinear aspects theorem", "nonlinear spectral theory"
"nonlinear partial theory" » "nonlinear particle theory", "nonlinear spatial theory", "nonlinear particles theory"

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: (((("nonlinear potential theory") OR ("nonlinear partial theory"))) OR ("nonlinear spectral theorem")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"nonlinear potential theory\") OR (\"nonlinear partial theory\"))) or (\"nonlinear spectral theorem\"))".
• Removing quotes may allow a broader search: (((( nonlinear potential theory ) OR ( nonlinear partial theory ))) or ( nonlinear spectral theorem )).
• Adding a wildcard symbol may retrieve word variants: (((("nonlinear potential theory") OR ("nonlinear partial theory"))) or ("nonlinear spectral theorem"))*.