
theorem Th13:
  for L being non empty 1-sorted, N being non empty NetStr over L
  for i being Element of N holds the carrier of N|i c= the carrier of N
proof
  let L be non empty 1-sorted, N be non empty NetStr over L, i be Element of N;
  let x be object;
  assume x in the carrier of N|i;
  then ex y being Element of N st y = x & i <= y by Def7;
  hence thesis;
end;
