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 to survey a wide and varied range of resources, we selected a sample data based on the bibliographic references of articles contained in 4 journals - all indexed by the ISI Web of Science and with an Impact Factor over the last three years - and two proceedings of international conferences held in 2012 and 2014.