private NegraPennTreeReaderFactory treeReaderFactory;
public TreeReaderFactory treeReaderFactory() {
if(treeReaderFactory == null)
treeReaderFactory = new NegraPennTreeReaderFactory(nodeCleanup, treeNormalizerInsertNPinPP, treeNormalizerLeaveGF, treebankLanguagePack());
return treeReaderFactory;
}