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R32 matrices????

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Dear All, 
I have a non-CCP4 crystallography question.  Recently I
measured data from some well characterized crystals which are members of
the space group R32.  Due to some problems with the integration program,
the data were integrated as C2.  I was not worried because I knew that
table 5.1 of the International Tables for Crystallography vol A ( the
1995 revised 4th edition) contained the appropriate matrices to convert
from C2 to R32 and vice versa.  However I could not successfully reindex
my data
with any variation of any of these matrices.  Finally, I had to find
someone cleverer than myself to derive the appropriate matrix which is

 0.5 0.5 0  
-0.5 0.5 0  
   1 0   3   

When this matrix is multiplied by the 3x1 matrix of h,k,l it reindexes
C2 data 
as R32 in the triple obverse setting. This matrix is not one of these
ones in 
table 5.1.

My question is:  what do the matrices in the international tables do?  I
can't believe that they are actually incorrect; I'm assuming I'm just
not understanding their function properly!  Is the matrix above
mathematically related in some way to one of the matrices in the table? 
Can anyone enlighten me and satisfy my curiosity about this matter?



Sarah Gillmor Hymowitz