The revised pdf file available here includes a line of LIST 1.2 which was omitted
from the published version. This item consists of the unitary ovoid in O+(8,5).
The original proof of LEMMA 2.2 also contained an incorrect definition of k0 (which should read k0 = (i+j)r–2ij); later in the proof, it should be clear that k0 is not divisible by r (rather than r2 as stated).
If you find additional errors or have comments, please email me ().