reserve x,y,z for object,
  i,j,n,m for Nat,
  D for non empty set,
  s,t for FinSequence,
  a,a1,a2,b1,b2,d for Element of D,
  p, p1,p2,q,r for FinSequence of D;

theorem
  <*<*a1,a2*>*> is Matrix of 1,2,D
proof
  <*a1,a2*> is FinSequence of D & len <*a1,a2*> =2 by FINSEQ_1:44;
  hence thesis by Th11;
end;
