On page 292 line 3 we incorrectly state that that the automorphism group of the projective space PG_m-1(q) is the projective linear group PGL_m(q) . This happens to be true when q=2, which is our assumption throughout the paper, except for Theorem 1.1. The reader can check that the only property of PGL_m(q) that we use in the proof of Theorem 1.1 is that it acts transitively on PG_m-1(q) , so the proof is still valid.

We do not need to know what the automorphism group is, but for the sake of completeness we mention that it is given by the fundamental theorem of projective geometry:

Aut(PG_m-1(q)) is the semi-direct product of the projective linear group PGL_m(q) with the automorphism group of the field Aut(F_q) (which acts co-ordinate-wise on vectors over F_q ).

Thanks to Richard Wilson for this correction.