reserve p,p1,p2,q,r,F,G,G1,G2,H,H1,H2 for ZF-formula,
  x,x1,x2,y,y1,y2,z,z1,z2,s,t for Variable,
  a,X for set;

theorem Th62:
  Free All(x,p) = Free p \ {x}
proof
A1: the_scope_of All(x,p) = p by Th8;
  All(x,p) is universal & bound_in All(x,p) = x by Th8;
  hence thesis by A1,ZF_MODEL:1;
end;
