OpenGrey: "System for Information on Grey Literature in Europe"
OpenGrey is an open access, open science tool, information system for locating Open Grey Literature in Europe. OpenGrey contains 700,000+ bibliographic references of grey literature (paper) produced in Europe and allows you to export and locate the documents. Open Grey Literature include technical or research reports, doctoral dissertations, conference papers, some official publications, and other grey literature. OpenGrey covers Science, Technology, Economics, Social Sciences, and Humanities.