Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for identifying topical entities. In one aspect, a method includes obtaining a plurality of entities that are associated with a first resource; for one or more of the identified entities, receiving search results for a search query derived from the entity; determining that search results for a search query including a particular entity include a specific type of search results; and determining that the particular entity is a topical entity of the first resource based at least in part on the particular entity appearing in a title or a resource locator of the first resource, wherein the topical entity of the first resource represents a predominant topic of the first resource.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for generating additional content. In one aspect, a method includes identifying one or more central entities, wherein each central entity represents a topic of a first resource being presented in a user interface; generating one or more search queries, each of the one or more search queries being derived from one or more of the central entities; obtaining search results for the one or more search queries from a search engine; selecting resources relevant to the first resource from resources referenced by the obtained search results; generating additional content for presentation in a user interface element of the user interface based on the selected resources; and categorizing the generated additional content into a plurality of categories, wherein each category of additional content is displayed in a separate portion of the user interface element.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for identifying topical entities. In one aspect, a method includes obtaining a plurality of entities that are associated with a first resource; for one or more of the identified entities, receiving search results for a search query derived from the entity; determining that search results for a search query including a particular entity include a specific type of search results; and determining that the particular entity is a topical entity of the first resource based at least in part on the particular entity appearing in a title or a resource locator of the first resource, wherein the topical entity of the first resource represents a predominant topic of the first resource.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for identifying central entities. In one aspect, a method includes obtaining candidate entities for a first resource; filtering a first entity graph whose nodes represent different entities found in a plurality of resources to remove nodes that do not correspond to a candidate entity, wherein pairs of nodes in the filtered first entity graph that are connected by an edge correspond to pairs of candidate entities that are associated with the same resource; generating a second entity graph for the first resource from the filtered first entity graph, wherein the second entity graph does not include nodes from the filtered first entity graph that are not connected to other nodes in the filtered first graph; and identifying candidate entities that are represented by nodes in the second entity graph as being central entities for the first resource.