On page 292 line 3 we incorrectly state that that the automorphism group of the projective space PGm-1(q) is the projective linear group PGLm(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 PGLm(q) that we use in the proof of Theorem 1.1 is that it acts transitively on PGm-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(PGm-1(q)) is the semi-direct product of the projective linear group PGLm(q) with the automorphism group of the field Aut(Fq) (which acts co-ordinate-wise on vectors over Fq ).
Thanks to Richard Wilson for this correction.