ROW  +--+--+--+--+
     |A |B |C |D |       
1    |  |  |  |  |       
     +--+--+--+--+
     +--+--+--+--+
     |H |G |A |C |      
2    |  |  |  |  |       
     +--+--+--+--+
     +--+--+--+--+
     |E |F |G |H |       
3    |  |  |  |  |      
     +--+--+--+--+

1. Row 1 has four cards with different letters on each of the two sides.
2. Row 2 has the same four cards from Row 1, two of which have been turned over and, all four of which are in different positions.
3. Row 3 has the same four cards from Row 2, two of which have been turned over and, all four of which are in different positions relative to the positions they were in Row 1 and Row 2.

Which letter is on the other side of each of the four cards in row 3?