1. A method performed by one or more computers, the method comprising: maintaining an authoritative resources index that, for each entity of a plurality of entities, maps one or more authoritative resources to the entity, wherein each of the one or more authoritative resources is a resource whose occurrence in search results for a received search query has been determined to be an indicator that the received search query is directed to the entity; receiving a first search query from a user device; receiving search results for the first search query provided by a search engine, wherein each of the search results identifies a respective resource; determining that the first search query relates to a first entity of a first entity type based on determining that a count of search results for the first search query that identify resources that have been mapped to the first entity in the authoritative resources index exceeds a first threshold number; and in response to determining that the first search query relates to the first entity of the first entity type, transmitting information identifying one or more entities of a second entity type that have a predetermined relationship with the first entity to the user device as part of a response to the first search query.
1. A method performed by one or more computers, the method comprising: maintaining an authoritative resources index that, for each entity of a plurality of entities, maps one or more authoritative resources to the entity, wherein each of the one or more authoritative resources is a resource whose occurrence in search results for a received search query has been determined to be an indicator that the received search query is directed to the entity; receiving a first search query from a user device; receiving search results for the first search query provided by a search engine, wherein each of the search results identifies a respective resource; determining that the first search query relates to a first entity of a first entity type based on determining that a count of search results for the first search query that identify resources that have been mapped to the first entity in the authoritative resources index exceeds a first threshold number; and in response to determining that the first search query relates to the first entity of the first entity type, transmitting information identifying one or more entities of a second entity type that have a predetermined relationship with the first entity to the user device as part of a response to the first search query. 5. The method of claim 1 , further comprising: ordering the one or more entities of the second entity type based at least in part on data that identifies, for each of the one or more entities of the second entity type, how frequently the entity is searched for by users after submitting a query directed to the first entity.