Collisional broadening and shift of Doppler-free two-photon thallium lines perturbed by rare-gas atoms A. Bielski, R. Ciuryło, J. Domysławska and R. S. Trawiński Eur. Phys. J. D, 5 3 (1999) 357-362 Published online: 15 March 1999 DOI: 10.1007/PL00021601