5. The method of claim 1 , further comprising: identifying a second set of features based on the second set of documents; determining if the second set of features are associated with the entity; and responsive to determining that the second set of features are associated with the entity, identifying a third set of documents based on a third model and the second set of features, each document of the third set of documents comprising a sufficient number of features in common with the second set of features to identify a document referring to the entity according to the third model.
5. The method of claim 1 , further comprising: identifying a second set of features based on the second set of documents; determining if the second set of features are associated with the entity; and responsive to determining that the second set of features are associated with the entity, identifying a third set of documents based on a third model and the second set of features, each document of the third set of documents comprising a sufficient number of features in common with the second set of features to identify a document referring to the entity according to the third model. 7. The method of claim 5 , wherein the first set of features includes at least one feature not included in the second set of features.