Burickson, Sherwin
      
      
         Philosophical Library, 1959
       Buku Referensi
   
Keylor, William R., 1944-
      
      
         Oxford University Press, 1996
       Buku Teks SO
   
Palmer, Alan
      
      
         Penguin Books , 1987
       Buku Referensi
   
Grenville, J.A.S.
      
      
         Routledge, 2005
       Buku Teks SO
   
Shuter, Paul
      
      
         Heineman Educational, 1988
       Buku Teks SO