* separar palavras-chave com vírgula
Melhores sites Environment 1-15:
1.
washingtonpost.com 
508,315

2.
abc.net.au 
403,286

3.
nationalgeographic.com 
317,150

4.
green.chem.cmu.edu 
305,027

5.
msu.edu 
282,033

6.
usgs.gov 
255,521

7.
fao.org 
254,797

8.
sciencedaily.com 
232,759

9.
popsci.com 
162,178

10.
sudaneseonline.com 
110,264

11.
esa.int 
81,187

12.
wn.com 
72,077

13.
wto.org 
60,252

14.
digitaljournal.com 
56,735

15.
think.mtv.com 
52,029

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