Perhaps you should try some spelling variations:
"collinear particles theory" » "collider particle theory", "colloidal particles theory", "colliding particles theory", "collinear particle theory", "collinear particles through"
"nonlinear vortices theory" » "nonlinear lattices theory", "nonlinear forces theory", "nonlinear vortex theory", "nonlinear services theory"
"nonlinear material theory" » "nonlinear materials theory", "nonlinear matrix theory", "nonlinear media 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 ((("collinear particles theory") OR ((("nonlinear vortices theory") OR ("nonlinear optics theory"))))))) OR ("nonlinear material theory")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"nonlinear partial theory\") or (((\"collinear particles theory\") or (((\"nonlinear vortices theory\") OR (\"nonlinear optics theory\"))))))) or (\"nonlinear material theory\"))".
• Removing quotes may allow a broader search: (((( nonlinear partial theory ) or ((( collinear particles theory ) or ((( nonlinear vortices theory ) OR ( nonlinear optics theory ))))))) or ( nonlinear material theory )).
• Adding a wildcard symbol may retrieve word variants: (((("nonlinear partial theory") or ((("collinear particles theory") or ((("nonlinear vortices theory") OR ("nonlinear optics theory"))))))) or ("nonlinear material theory"))*.