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 optics theory", "nonlinear lattices theory", "nonlinear forces theory", "nonlinear vortex theory", "nonlinear services theory"
"nonlinear material theory" » "nonlinear materials theory", "nonlinear matrix theory", "nonlinear partial theory"
"nonlinear spatial theory" » "nonlinear partial theory", "nonlinear spectral theory", "nonlinear static theory", "nonlinear special theory", "nonlinear social theory", "nonlinear spatial memory"

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

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