I am working on a longer blog post about a project I created in 2018 about Norwegian Correspondences (NorKorr), linking the collections of letters and other correspondence materials in Norwegian cultural heritage institutions and other institutions that archive and curate such materials by making use of the CorrespSearch framework.
In the meantime, you may take a look at the paper “Norwegian Correspondences and Linked Open Data” that was published in the DHN2019 conference proceedings. You may also want to check out the GitHub repository for NorKorr and read about project-related activities on the NorKorr website.