Knowledge systems and prolog  a logical approach to expert systems and natural language processing 
Adrian Walker ... (et al.) 
 - Reading, Mass.  Addison-Wesley  1987 
 - 474 p. : ill. ; 24 cm. 
<br/><br/>p. 449-457 
<br/><br/><label>ISBN: </label>0201090449 
<br/><br/><label>LCCN: </label>86-22126 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Expert systems (Computer science)<br/>Prolog (Computer program language)