My RI - Measuring your Research Impact.
There are lots of studies in the literature which have compared the value of our three tools when using them to measure research output and impact in various disciplines, for example:
Etxebarria, G. and Gomez-Uranga, M. 2010. Use of Scopus and Google Scholar to measure social sciences production in four major Spanish universities. Scientometrics, 82(2), pp. 333-349.
Mikki, S. 2010. Comparing Google Scholar and ISI Web of Science for Earth sciences. Scientometrics, 82(2), pp. 321-331.
Yang, K. and Meho, L.I. 2006. Citation Analysis: A comparison of Google Scholar, Scopus, and Web of Science. Proceedings of the American Society for Information Science & Technology, 43(1), pp. 1-15.
My RI by University College Dublin, Dublin City University, Dublin Institute of Technology, The National University of Ireland, Maynooth and the NDLR adapted by Marion Kelt, Glasgow Caledonian University is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at http://www.ndlr.ie/myri/.