The JHOVE PDF module, which I wrote, sometimes reports that documents are invalid because they have self-recursive page trees, although other applications can open these documents. In examining one of these documents more closely, I found that the top-level node of its page tree contains a reference to itself (i.e., the same PDF object), thus triggering infinite recursion. Is this considered a legitimate form of the page tree? Are there other cases of apparent self-recursion in page trees which are actually legitimate?
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