The commentary by Larsen, while raising some valid points about counting methods for publications analysis, is largely irrelevant in the context of the aims and conclusions of the article by Seymour et al. Different counting methods were used for the second output indicator-patents-which avoided any possibility of double counting and showed the same trends. Any overstatement of the number of publications produced in the EU25+ countries would only serve to reinforce the conclusions of the original article. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.