中心地的等级越高，其服务的区域越大，此类中心地的数量越少。
Innovation in forestry begins with respecting traditional wisdom.
A whole stack of memories never equal one little hope.
The universe would look to a two-dimensional creature who spend its life moving on the service of what turned out to be a globe， it could travel for millions of years and would always return to its starting point， it would never be conscious of what was above it or beneath it.