Doppler limited laser spectroscopy on hafnium lines. Part I: Hyperfine structure of even-parity levels S. Bouazza, M. Fienhold, G. H. Guthöhrlein, H. O. Behrens and J. Dembczynski Eur. Phys. J. D, 6 3 (1999) 303-309 Published online: 15 June 1999 DOI: 10.1007/s100530050313