Perhaps you should try some spelling variations:
"multivariate problems model" » "multiscale problems model", "multivariate probability model"
"multivariate public model" » "multivariate public money", "multivariate public moral", "multivariate public more"

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: "((\"multivariate problems model\") OR (\"multivariate public model\"))".
• Removing quotes may allow a broader search: (( multivariate problems model ) OR ( multivariate public model )).
• Adding a wildcard symbol may retrieve word variants: (("multivariate problems model") OR ("multivariate public model"))*.