Heterodyne refractometer and air wavelength reference at 633 nm S. Topçu, Y. Alayli, J.-P. Wallerand and P. Juncar Eur. Phys. J. Appl. Phys., 24 1 (2003) 85-90 Published online: 29 September 2003 DOI: 10.1051/epjap:2003070