Research theses (PhD, Professional Doctorates etc) are excellent sources of unpublished information. Two key places to start searching are SURE (our Sunderland repository of research outputs) for University of Sunderland theses and EThOS the UK’s national thesis service:
Note: This database is not currently available due to the British Library cyber attack.
”The aim of EThOS is to offer a 'single point of access' where researchers the world over can access ALL PhD theses produced by UK Higher Education. An increasing number of UK HE theses are already available here in full text.
Sources for theses from other parts of the world include: