Hello,   
      
   I'm reading Compiler Construction, by Niklaus Wirth, available on   
   http://www.oberon.ethz.ch/WirthPubl/CBEAll.pdf and on page 9 he shows   
   this little piece of BNF:   
      
   E = T | A "+" T.   
   T = F | T "*" F.   
   F = V | "(" E ")".   
   V = "a" | "b" | "c" | "d".   
      
   A is being used on the right hand side without it being defined on the   
   left hand side first. What am I missing?   
      
   The only thing I can think of is that it is missing a production at   
   first, like:   
      
   A = E   
      
   >From this BNF it writes this "programs" (on page 10):   
      
   a*b+c   
   a+b*c   
   (a+b)*(c+d)   
      
   Thanks.   
      
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