Perhaps you should try some spelling variations:
"collinear particles theory" » "collider particle theory", "colloidal particles theory", "colliding particles theory", "collinear particles through"
"nonlinear particle theory" » "linear particle theory", "nonlinear price theory", "nuclear particle theory"
"nonlinear material theory" » "nonlinear materials theory", "nonlinear matrix theory", "nonlinear media theory"
"nonlinear partial theory" » "nonlinear spatial theory", "nonlinear partial tears", "nonlinear partial theta"

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 particle theory") OR ("collinear particles theory"))))) OR ("nonlinear material theory")).
• Removing quotes may allow a broader search: (((( nonlinear partial theory ) or ((( nonlinear particle theory ) or ( collinear particles theory ))))) or ( nonlinear material theory )).
• Adding a wildcard symbol may retrieve word variants: (((("nonlinear partial theory") or ((("nonlinear particle theory") or ("collinear particles theory"))))) or ("nonlinear material theory"))*.