sentence1: coordination is a common syntactic phenomena and work has been done to improve coordination structures predication in the general case ( cite-p-9-4-2 , cite-p-9-4-1 , cite-p-9-4-8 , cite-p-9-4-6 ) .
sentence2: coordination is a common syntactic phenomena , appearing in 38.8 % of the sentences in the penn treebank ( ptb ) ( cite-p-24-1-13 ) , and in 60.71 % of the sentences in the genia treebank ( cite-p-24-1-15 ) .