Perhaps you should try some spelling variations:
"nonlinear particles theory" » "collinear particles theory", "nonlinear vortices theory", "nonlinear martingales theory", "nonlinear particle theory", "nonlinear particles through"
"nonlinear material theory" » "nonlinear materials theory", "nonlinear media theory"
"nonlinear matrix theory" » "linear matrix theory", "nonlinear materials theory", "nonlinear media theory"
"nonlinear water theory" » "nonlinear waves theory", "nonlinear wave theory", "nonlinear filter theory", "nonlinear matter theory", "nonlinear layer theory", "nonlinear laser theory"
"nonlinear partial theory" » "nonlinear particle theory", "nonlinear spatial theory", "nonlinear partial memory"

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