reserve x for set,
  D for non empty set,
  k,n,m,i,j,l for Nat,
  K for Field;

theorem Th33:
  for s1,s2,s3 be FinSequence st 
  len s1 = n & len s2 = n & len s3 = n holds <*s1,s2,s3*> is tabular
proof
  let s1,s2,s3 be FinSequence;
  assume
A1: len s1 = n & len s2 = n & len s3 = n;
  now
    take n;
    let x be object;
    assume x in rng (<*s1,s2,s3*>);
    then
A2: x in { s1,s2,s3} by FINSEQ_2:128;
    then reconsider r=x as FinSequence by ENUMSET1:def 1;
    take r;
    thus x= r & len r=n by A1,A2,ENUMSET1:def 1;
  end;
  hence thesis;
end;
