Evidence for calcium soaps in human hair shaft revealed by sub-micrometer X-ray fluorescence F. Briki, C. Mérigoux, F. Sarrot-Reynauld, M. Salomé, B. Fayard, J. Susini and J. Doucet J. Phys. IV France, 104 (2003) 337-340 DOI: 10.1051/jp4:200300094