Perhaps you should try some spelling variations:
"more centralized distributed" » "more decentralized distributed", "more constrained distributed", "more centric distributed", "more generalized distributed", "models centralized distributed", "non centralized distributed"
"maize fertilizer distributed" » "maize fertilizer distributor", "maize certified distributed", "maize penalized distributed", "base fertilizer distributed", "more fertilizer distributed", "rate fertilizer distributed"

Try widening your search to All Fields.

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: (("more centralized distributed") OR ("maize fertilizer distributed")).
• Removing quotes may allow a broader search: (( more centralized distributed ) or ( maize fertilizer distributed )).
• Adding a wildcard symbol may retrieve word variants: (("more centralized distributed") or ("maize fertilizer distributed"))*.