They are too old for Math Reviews, but I think the articles in question are:

 - Von Neumann: "Zur Prüferischen Theorie der idealen Zahlen", Acta Scientiarum Mathematicum (Szeged) 2:4 (1926) (can be read online at <a href="http://acta.fyx.hu/acta/showCustomerVolume.action?id=5089&dataObjectType=volume&noDataSet=true&style=">the journal's website</a>)

 - Prüfer: "Neue Begründung der algebraischen Zahlentheorie", Math. Annalen 94 (1925), 198-243 (a link to volume 94 of the journal is at the Göttingen archive <a href="http://gdz.sub.uni-goettingen.de/dms/load/img/?PPN=PPN235181684_0094">here</a>)

in both of which one main idea seems to be (in modern language) to consider the embedding of a ring of integers $\frak{o}$ into the product $ \prod_{\frak{p},n}\frak{o}/\frak{p}^n$. The Von Neumann paper even mentions the $p$-adics. That's about all I could extract at a glance, my German being virtually nonexistent - someone with better German will be able do a more thorough job.