Jeanne Hazzard and Stephanie Towery have published "Workflow Development for an Institutional Repository in an Emerging Research Institution" in the Journal of Librarianship and Scholarly Communication.
Here's an excerpt:
We discovered that our faculty retain nearly none of their pre-print or post-print versions of their published articles, and so we are unable to archive those titles in the repository. Nearly 47% of the articles found were in green journals that allow only pre- or post-print copies. Most faculty were unable to produce versions of their work other than the publisher’s PDF, which many publishers restrict from upload into a repository.