1. A method performed by one or more computers, the method comprising: receiving a first search query from a user device, wherein the first search query has been determined to relate to a first entity of a first entity type, and wherein one or more entities of a second entity type have a predetermined relationship with the first entity; receiving search results for the first search query provided by a search engine, wherein each of the search results identifies a respective resource; determining, from the search results, whether or not to include information identifying the one or more entities of the second entity type as part of a response to the first search query, comprising: determining that a count of search results identifying a resource containing a reference to the first entity satisfies a first threshold value, determining that a count of search results identifying a resource having the second entity type as a relevant entity type satisfies a second threshold value, and determining to include information identifying the one or more entities of the second entity type as part of the response to the first search query based on determining that the count of search results identifying the resource containing the reference to the first entity satisfies the first threshold value and determining that the count of search results identifying the resource having the second entity type as a relevant entity type satisfies the second threshold value; and transmitting information identifying the one or more entities of the second entity type to the user device as part of the response to the first search query.
1. A method performed by one or more computers, the method comprising: receiving a first search query from a user device, wherein the first search query has been determined to relate to a first entity of a first entity type, and wherein one or more entities of a second entity type have a predetermined relationship with the first entity; receiving search results for the first search query provided by a search engine, wherein each of the search results identifies a respective resource; determining, from the search results, whether or not to include information identifying the one or more entities of the second entity type as part of a response to the first search query, comprising: determining that a count of search results identifying a resource containing a reference to the first entity satisfies a first threshold value, determining that a count of search results identifying a resource having the second entity type as a relevant entity type satisfies a second threshold value, and determining to include information identifying the one or more entities of the second entity type as part of the response to the first search query based on determining that the count of search results identifying the resource containing the reference to the first entity satisfies the first threshold value and determining that the count of search results identifying the resource having the second entity type as a relevant entity type satisfies the second threshold value; and transmitting information identifying the one or more entities of the second entity type to the user device as part of the response to the first search query. 2. The method of claim 1 , wherein each of the search results includes a respective title and a respective snippet of text extracted from the respective resource identified by the search result, and wherein determining that the count of search results identifying a resource containing a reference to the first entity satisfies the first threshold value comprises: determining that a count of search results that include a reference to the first entity in the respective title or the respective snippet of text included in the search result satisfies the first threshold value.