[The following paragraph of AS 1205 was effective for audit reports issued between December 31, 2016, and June 30, 2017. The current standard can be found here.]
.03 If the auditor decides that it is appropriate for him to serve as the principal auditor, he must then decide whether to make reference in his report2 to the audit performed by another auditor. If the principal auditor decides to assume responsibility for the work of the other auditor insofar as that work relates to the principal auditor's expression of an opinion on the financial statements taken as a whole, no reference should be made to the other auditor's work or report. On the other hand, if the principal auditor decides not to assume that responsibility, his report should make reference to the audit of the other auditor and should indicate clearly the division of responsibility between himself and the other auditor in expressing his opinion on the financial statements. Regardless of the principal auditor's decision, the other auditor remains responsible for the performance of his own work and for his own report.
2 See paragraph .09 for example of appropriate reporting when reference is made to the audit of other auditors.