Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for performing actions of determining that one or more in-depth article search results are to be provided in response to a query, obtaining a topicality score for each in-depth article of a plurality of in-depth articles, each topicality score indicating a degree of relevance of a respective in-depth article to the query, obtaining a document score for each in-depth article of the plurality of in-depth article, each document score being based on a respective topicality score and a respective in-depth article score, selecting one or more in-depth articles from the plurality of in-depth articles based on respective document scores, and providing the one or more in-depth article search results for display, each in-depth article search result representing an in-depth article of the one or more in-depth articles.

Abstract: Methods, systems, and apparatus, including computer programs encoded on computer storage media, for classifying documents. One of the methods includes obtaining a collection of training documents, the training documents including positive documents identified as being longform documents and negative documents identified as not being longform documents; extracting one or more features from the training documents, wherein the features represent lexical or textual content of the training documents; and generating a longform document classifier trained using feature instances extracted from the training documents, wherein the generated longform document classifier is trained such that input documents are classified as being longform documents or classified as not being longform documents.

Abstract: Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for performing actions of determining that one or more in-depth article search results are to be provided in response to a query, obtaining a topicality score for each in-depth article of a plurality of in-depth articles, each topicality score indicating a degree of relevance of a respective in-depth article to the query, obtaining a document score for each in-depth article of the plurality of in-depth article, each document score being based on a respective topicality score and a respective in-depth article score, selecting one or more in-depth articles from the plurality of in-depth articles based on respective document scores, and providing the one or more in-depth article search results for display, each in-depth article search result representing an in-depth article of the one or more in-depth articles.