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on PageRank index 
.
Left panel : Data for different species for word length of 6-letters: bull BT (magenta), dog CF (red), elephant LA (green), Homo sapiens HS (blue) and zebrafish DR (black). Right panel : Data for HS (full curve) and LA (dashed curve) for word length 
(brown), 
(blue/green), 
(red).
