For this purpose we performed a 10-fold cross validation experiment on the baseNP training data, sections 15-18 of the WSJ part of the Penn Treebank (211727 tokens). Like the data used by <cite>(Ramshaw and Marcus, 1995)</cite> , this data was retagged by the Brill tagger in order to obtain realistic part-of-speech (POS) tags 3. The data was segmented into baseNP parts and non-baseNP parts in a similar fashion as the data used by <cite>(Ramshaw and Marcus, 1995)</cite> .