In many papers dealing with topological Hochschild homology, the original unpublished manuscripts by Bökstedt are cited. To name one example, in McClure and Staffeldt's *On the topological Hochschild homology of $bu$*, 1989, we can see

>Topological Hochschild homology (Preprint, 1987)

>Topological Hochschild homology of $\mathbb Z$ and $\mathbb Z/p$ (Preprint, 1987)

>The natural transformation form $K(\mathbb Z)$ to $THH(\mathbb Z)$ (Preprint, 1987).

On Angeltveit & Rognes' *Hopf algebra structure on topological Hochschild homology*  only the first two are cited, but are attributed to "ca. 1986" and to the University of Bielefeld.

On Vogt's *Introduction to algebra over "brave new rings"*, again, only the first two appear, and attributed to 1985. And the list could go on.

Anyway, the question is, where could one get hold of these preprints?