Following are few Co-reference resolution tools:
"Reconcile is an automatic coreference resolution system that was developed to provide a stable test-bed for researchers to implement new ideas quickly and reliably. It achieves roughly state of the art performance on many of the most common coreference resolution test sets, such as MUC-6, MUC-7, and ACE. Reconcile comes ready out of the box to train and test on these common data sets (though the data sets are not provided) as well as the ability to run on unlabeled texts. Reconcile utilizes supervised machine learning classifiers from the Weka toolkit, as well as other language processing tools such as the Berkeley Parser and Stanford Named Entity Recognition system. The source language is Java, and it is freely available under the GPL."