Reference private resources in paper
part of an algorithm on my paper is based on work described on one of those private documents. I need to acknowledge that somehow.


The algorithm has not previously been published, so you can claim that it is an original contribution of your paper. You can acknowledge the project in your acknowledgements section.

Problems might arise if your paper and the private document have different authors. In this case, you should seek permission from those authors to publish your paper and you should acknowledge the contribution of those authors.