Grey Literature citations in the age of Digital Repositories and Open Access

The work measures grey citations in the years 2012, 2013 and 2014 and then describes the features of GL documents cited in different areas of knowledge: Computational Linguistics, Computer Science and Engineering. With the aim of surveying a wide and varied range of resources, we selected a sample data based on the bibliographical references of articles contained in four journals - all indexed by Scopus Citation Database and ISI Web of Science, with an Impact Factor (IF) over the last three years - and two proceedings of international conferences held in 2012 and 2014.