Photon and particle interactions with surfaces in space / proceedings of the Eslab Symposium, held at Noordwijk, The Netherlands, 26-29 September, 1972 ; ed. by R.J.L. GrardPhoton and particle interactions with surfaces in space : proceedings of the 6th Eslab Symposium, held at Noordwijk, The Netherlands, 26-29 september, 1972 / ed. by R. J. L. Grard