21.   Usatenko says finding and studying the graves would not be difficult, but that bureaucratic barriers are preventing it.

22.   While technological gains have smashed real communication costs, however, trade barriers have prevented this being passed on to the consumer.

n. + prevent >>共 1376
police 4.55%
law 4.20%
rule 2.33%
step 2.29%
action 2.16%
weather 1.98%
authority 1.78%
government 1.54%
injury 1.50%
problem 1.17%
barrier 0.41%
barrier + v. >>共 183
be 36.43%
fall 4.27%
remain 4.27%
come 4.15%
prevent 2.76%
keep 2.39%
go 2.26%
exist 1.88%
have 1.76%
make 1.26%
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