The redistribution of between 4 x 1014 and 6 x 1014/cm2 of atoms on a clean (111) surface, during the reversible 7 x 7 to 1 x 1 transition, was revealed by a shifting of monatomic steps and a change in size of 2-dimensional islands.

A.V.Latyshev, A.B.Krasilnikov, A.L.Aseev, L.V.Sokolov, S.I.Stenin: Surface Science, 1991, 254[1-3], 90-6