and disclose its factual contents. See 5 U.S.C. § 552(b); Maricopa Audubon Soc’y, 108 F.3d at 1092. The burden is on the agency to establish that all reasonably segregable portions of a document have been segregated and disclosed. 5 U.S.C. § 552(a)(4)(B), (b). “Courts must apply that burden with an awareness that the plaintiff, who does not have access to the withheld materials, is at a distinct disadvantage in attempting to controvert the agency’s claims.” Maricopa Audubon Soc’y, 108 F.3d at 1092 (internal quotation omitted). The agency can meet its burden by offering an affidavit with reasonably detailed descriptions of the withheld portions of the documents and alleging facts sufficient to establish an exemption. Id.; see also Wiener v. FBI, 943 F.2d 972, 979 (9th Cir.1991) (<HOLDING>). The affidavits must not be conclusory. Church
holding that it was appropriate for the district court to refer to the documents attached to the motion to dismiss since the documents were referred to in the complaint holding that pursuant to the best evidence rule trial testimony relying on documents was inadmissible without submission of such documents or an explanation as to why the documents were unavailable holding that the agency did not have an obligation to search for and produce the documents the plaintiff claimed entitlement to because the plaintiffs foia request gave no indication that she sought those particular documents holding an agency need not demonstrate that all responsive documents were found and that no other relevant documents could possibly exist holding that the fbis explanation was not sufficiently specific when it provided no information about particular documents and portions of documents that might be useful in contesting nondisclosure