reserve A,B,C for Ordinal;
reserve a,b,c,d for natural Ordinal;
reserve l,m,n for natural Ordinal;

theorem Th10:
  for n,m st {} in m & n divides m holds n c= m
proof
  let n,m such that
A1: {} in m;
  given a being Ordinal such that
A2: m = n*^a;
  a <> {} by A1,A2,ORDINAL2:38;
  hence thesis by A2,ORDINAL3:36;
end;
