Sales Tax ; Precision Pools P/L v. Commission of Taxation (unreported, 10 September1992, QG 90/92, Spender J.) ; Somenco (No. 87) P.L v. Commissioner of Taxation (unreported, 20 November1992, NG 768/91, FC) ; Mutual Pools and Staff P/L v. Commissioner of Taxation (1992) 66 A.L.J.R. 222 ;