1. A system for integrating a specialized knowledge source into a general search service, comprising: a search engine interface to receive a search query having search terms from a user; an expert knowledge engine configured to enable retrieval of expert search results; a predictive model module configured to generate a predictive model that provides a measure of the likelihood that the expert knowledge engine can provide valuable information for the search query; a query reformulation module to reformulate a query for use by the expert knowledge engine; and a display module configured to display the expert search results to the user.