The dates on the supporting documents go back to the years before 1990 and is not possible to verify that the quantities and rates are restricted to the materials that were on-site (un-fixed) as at 2 August 1990.
证明文件上的日期回溯至1990年以前的几年，因此无法查证其数量和价率是否仅属于1990年8月2日在现场(不固定)的物料。