The NASA Astrophysics Data System: The Search Engine and its User   Interface
  The ADS Abstract and Article Services provide access to the astronomical literature through the World Wide Web (WWW). The forms based user interface provides access to sophisticated searching capabilities that allow our users to find references in the fields of Astronomy, Physics/Geophysics, and astronomical Instrumentation and Engineering. The returned information includes links to other on-line information sources, creating an extensive astronomical digital library. Other interfaces to the ADS databases provide direct access to the ADS data to allow developers of other data systems to integrate our data into their system.   The search engine is a custom-built software system that is specifically tailored to search astronomical references. It includes an extensive synonym list that contains discipline specific knowledge about search term equivalences.   Search request logs show the usage pattern of the various search system capabilities. Access logs show the world-wide distribution of ADS users.   The ADS can be accessed at http://adswww.harvard.edu 
G. Eichhorn, M. J. Kurtz, A. Accomazzi, C. S. Grant and S. S. Murray   (Harvard-Smithsonian Center for Astrophysics, Cambridge)