Modulation-free pump-probe spectroscopy of strontium atoms C. Javaux, I.G Hughes, G. Lochead, J. Millen and M. P.A. Jones Eur. Phys. J. D, 57 2 (2010) 151-154 Published online: 16 February 2010 DOI: 10.1140/epjd/e2010-00029-4