Is it acceptable to use non-English references in a computer science paper? I am currently reviewing an interdisciplinary computer science paper which is heavily based on previous works in logistics and process engineering that have been unfortunately published only in German (18 out of total 30 references). The overall idea is sound, but as the logistics structures are in some sense a basis of the paper, I have a strong inclination to reject the manuscript as the research cannot be followed and reconstructed by a researcher that does not understand German.

On top of that, virtually none of them are available online, or otherwise easily accessible.

I was going to hit the "Reject" button just a few moments ago, but I still have my doubts: I know that in humanities and also in mathematics people often cite publications written in other languages, but I have not yet seen something like that in computer science. Also, if it were one or two references, but 60%? The journal reviewing policy does not help me in this case.

I was thinking about proposing the following workarounds:


Extending the paper - this is probably not an option as the journal imposes quite a strong page limit, or
A supplementary report - the vital parts of the non-English text could be made available as an Technical Report or an on-line publication (I was thinking about arXiv) and this can be referenced in the manuscript.


Is it fair to reject it? Has anyone experienced something similar? What was your decision?
Having many non-English references is absolutely no valid reason to reject a computer science paper. 

If a reader wants to follow up on the references, they can learn some German, find a translator, etc. But this is the responsibility of the reader, not the author.