Perhaps you should try some spelling variations:
land development » world development, child development
radiation rates » graduation rates, radiation images, radiation status
technology 6.4 » technology 6.3, technology 2.4, technology 6.1
6.4 radiation » 3.4 radiation, 10.4 radiation, 2.1 radiation
costs land » cost land, costly land, costs canada
dr et » fr et, ur et
dr em » dm em

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: "technology 6.4 radiation rates ((dr et) OR (dr em)) communication costs land development 1 africa.~".
• Adding a wildcard symbol may retrieve word variants: technology 6.4 radiation rates ((dr et) OR (dr em)) communication costs land development 1 africa.*.