Is a motion to dismiss based on the existence of a document that is not physically attached to the motion?

Second, under the doctrine of incorporation by reference, "[a] district court ruling on a motion to dismiss may consider documents whose contents are alleged in a complaint and whose authenticity no party questions, but which are not physically attached to the plaintiff's pleadings." Parrino v. FHP, Inc., 146 F.3d 699, 705 (9th Cir. 1998) (internal quotation marks omitted). The "incorporation by reference" doctrine has been extended "to situations in which the plaintiff's claim depends on the contents of a document, the defendant attaches the document to its motion to dismiss, and the parties do not dispute the authenticity of the document, even though the plaintiff does not explicitly allege the contents of that document in the complaint." Knievel v. ESPN, 393 F.3d 1068, 1076 (9th Cir. 2005).