@book{learnprolognow,
 author =    {Blackburn, Patrick and 
              Bos, Johan and 
              Striegnitz, Kristina},
 publisher = {College Publications},
 series =    {Texts in Computing},
 volume =    {7},
 title =     {Learn Prolog Now!},
 year =      {2006},
 isbn =      {1-904987-17-6},
}