Not all repositories have well developed search engines and metadata that support advancing searching, please use library indexes and academic search engines (Google Scholar) to find the exact title and author or even the right repository.
Subject/disciplinary repositories are a great way to quickly and widely disseminate results from the early stages of your research. Publishers allow you to formally publish these outputs as journal articles or chapters once they have been submitted for and passed peer-review. You can search for a relevant subject repository using the Directory of Open Access Repositories (OpenDOAR). Use the 'Advanced Search' function and tick the box for 'Disciplinary' repository type and then choose the subjects you are interested in.
Here are examples of some preprint servers and subject repositories
HEER (Higher Education Empirical Research). From the Open University Centre for Higher Education Research and Information (CHERI). Only CHERI-written summaries of the original research papers are OA through HEER.
OER Research. A repository for research on open educational resources (OERs).
