::03-XX   Mathematical logic and foundations  
   03-00   General reference works (handbooks, dictionaries, bibliographies, etc.)  
   03-01   Instructional exposition (textbooks, tutorial papers, etc.)  
   03-02   Research exposition (monographs, survey articles)  
   03-03   Historical (must also be assigned at least one classification number from Section 01)  
   03-04   Explicit machine computation and programs (not the theory of computation or programming)  
   03-06   Proceedings, conferences, collections, etc.  
  03Axx  Philosophical aspects of logic and foundations  
  03Bxx  General logic  
  03Cxx  Model theory  
  03Dxx  Computability and recursion theory  
  03Exx  Set theory  
  03Fxx  Proof theory and constructive mathematics  
  03Gxx  Algebraic logic  
  03Hxx  Nonstandard models [See also 03C62]