Investigations of the optical and thermal parameters of porous silicon layers with the two wavelength photoacoustic method M. Maliński, L. Bychto, A. Patryn, J. Gibkes, B.K. Bein and J. Pelzl J. Phys. IV France, 129 (2005) 241-243 DOI: 10.1051/jp4:2005129049