Worldwide Comparison of Lightning Impulse Voltage Measuring Systems at the 400-kV Level. - Jari K. Hällström; Martti M. Aro; Anders Bergman; V. Bovier-Lapierre; F. Garnacho; J. I. Juvik; V. Kiseliev; Z. Lian Hong; Wolfgang Lucas; Yi Li; M. L. Pykälä; Juris Rungis; et al. (IEEE Trans. Instrum. Meas., 2007)