Secondary soils (Heterochronogenous soils)
central underdeveloped area
economic undeveloped region
Economic undeveloped regions
Economically underdeveloped areas
economically underdeveloped region
economically undeveloped area
peasants in underdeveloped areas
Percentage of undeveloped grain
remote and undeveloped areas
the economically undeveloped areas
Underdeveloped area
欠发达地区
低度开发地区
经济欠发达地区
不发达地区
老少边穷地区
underdeveloped counties
underdeveloped countries
Underdeveloped economic regions