Air Technical Index documents

[HypersonicAero]

I'm a researcher in aerodynamics. I'm been spending some time doing a few detailed literature searches on select topics in aerodynamics, including wind tunnel testing of aerodynamic models. My searches have turned up a ton of wind tunnel data generated by the Germans during World War 2. To that end, I'm looking for quite a few original German aeronautics reports.

Many of the documents that I'm looking for are in NASM's captured document collection, but quite a few are not. These documents tend to have ATI numbers that identify them as part of the Air Technical Index collection of documents. This collection appears to consist of both captured German documents and original research done in the US. ATI documents were distributed by the predecessor to the US DoD's Defense Technical Information Center (DTIC). They predate the "AD" document series that they use to distribute documents now.

Does anyone know how to find ATI documents in libraries or archives? I haven't been able to find any way to reliably track down a given ATI document once I have its associated ATI number. It's straightforward to find "AD" documents at most university libraries, for example, but all ATI documents appear to be dead ends. I'd appreciate any tips or comments.