Auditing Functions for Internal Control Systems with Interdependent Documents and Channels
重新推导了Grimlund[1982]中因忽略并行文档间相互依赖关系而错误的审计函数，适用于处理采购订单与供应商发票等相互依赖文档的误差累积建模。
Grimlund [1982] has demonstrated how an function1 can be used to model the accumulation of errors in documents as they flow through an internal control system. He has derived expressions for for seven different internal control structures. However, the applicability of these functions is limited because of the exclusion of interdependencies among parallel documents in the treatment of cases (d) and (e) (Grimlund [1982, p. 331]). For example, in the preparation and review process of a voucher for determining the unit price and the amount to be paid, the two documents (a purchase order and a vendor's invoice) to be merged are not necessarily independent; an error in one may cause an error in the other. In fact, the auditing function for case (e) as derived by Grimlund is incorrect because the two parallel documents being merged in this case are not independent. The purpose of this note is to rederive the and the appropriate