1. A method performed by one or more computers, the method comprising: 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 from the search results that the first search query relates to a first entity of a first entity type; determining that one or more entities of a second entity type have a predetermined relationship with the first entity; and transmitting information identifying the one or more entities of the second type to the user device as part of a response to the first search query.