The paper:

I. M. Wanless, Jerrum's multistorey carpark, Austral. Math. Soc. Gaz., 23 (1996) 193-197.

is really just a preliminary announcement of the results from this paper:

I. M. Wanless, The Holens-Djokovic conjecture on permanents fails, Linear Algebra Appl. 286 (1999) 273-285.