1. M. Henzler: Surface Sci.25, 650 (1971)
2. W.P. Ellis, R.L. Schwoebel: Surface Sci.11, 82 (1968)
3. M. Henzler: Bull. Am. Phys. Soc. Ser. (11)14, 794 (1969); and Surface Sci.19, 159 (1970)
4. J. Perdereau, G.E. Rhead: In Coll. Int. Struct. Prop. Surfaces Solides (Edition CNRS, Paris, 1969) p. 37; and Surface Sci.24, 555 (1970)
5. M. Henzler: Surface Sci.22, 12 (1970)