Citation context has been explored in several studies (Nakov et al., 2004;Ritchie et al., 2006;Schwartz et al., 2007;Siddharthan and Teufel, 2007).
unlike in the case of ad hoc retrieval, we do not really have a query describing the impact of the paper; instead, we have a lot of citation contexts that can be used to infer information about the query.