Comment on ´nonexistence of certain perfect binary arrays´ and ´nonexistence of perfect binary arrays´ (by Jedwab and Davis, with reply)

For original papers see ibid., vol.29, p.99-101 (1993) and ibid., vol.27, p.1252-1254 (1991). The commenter suggests that the nonexistence of the 4*3*3*9 perfect binary array (PBA) can be easily proved, without the need for a lengthy computer search. He points out that the nonexistence of the 9*36 PBA and 18*18 PBA can also be proved. In reply, the original authors suggest that the commenter´s analysis is based on an incorrect lemma.