8. A system comprising: one or more processors; one or more computer-readable storage mediums containing instructions configured to cause the one or more processors to perform operations comprising: receiving a first query; receiving a second, follow-up query; determining that an anaphora is present in the second, follow-up query by determining that the second, follow-up query includes a pronoun that refers to an entity that is not present in the second, follow-up query; in response to determining that the anaphora is present in the second, follow-up query, determining that the first query is associated with a plurality of possible entities; generating a plurality of candidate queries, wherein each candidate query of the plurality of candidate queries is generated by replacing the pronoun in the second, follow-up query with a corresponding possible entity; obtaining a ranking for the plurality of candidate queries from a ranking engine; determining that a corresponding possible entity in a highest-ranked candidate query of the plurality of candidate queries is an entity associated with the anaphora from the second, follow-up query, wherein the entity associated with the anaphora from the second, follow-up query is the entity that is not present in the second, follow-up query and is referred to by the pronoun in the second, follow-up query; and based on determining that the corresponding possible entity in the highest-ranked candidate query is the entity associated with the anaphora, providing the highest-ranked candidate query to a search engine and obtaining search results for the highest-ranked candidate query from the search engine.
8. A system comprising: one or more processors; one or more computer-readable storage mediums containing instructions configured to cause the one or more processors to perform operations comprising: receiving a first query; receiving a second, follow-up query; determining that an anaphora is present in the second, follow-up query by determining that the second, follow-up query includes a pronoun that refers to an entity that is not present in the second, follow-up query; in response to determining that the anaphora is present in the second, follow-up query, determining that the first query is associated with a plurality of possible entities; generating a plurality of candidate queries, wherein each candidate query of the plurality of candidate queries is generated by replacing the pronoun in the second, follow-up query with a corresponding possible entity; obtaining a ranking for the plurality of candidate queries from a ranking engine; determining that a corresponding possible entity in a highest-ranked candidate query of the plurality of candidate queries is an entity associated with the anaphora from the second, follow-up query, wherein the entity associated with the anaphora from the second, follow-up query is the entity that is not present in the second, follow-up query and is referred to by the pronoun in the second, follow-up query; and based on determining that the corresponding possible entity in the highest-ranked candidate query is the entity associated with the anaphora, providing the highest-ranked candidate query to a search engine and obtaining search results for the highest-ranked candidate query from the search engine. 13. The system of claim 8 wherein the ranking engine ranks the plurality of candidate queries by ranking n-grams contained within the candidate queries.