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    function f = thisissos(Hd)
%THISISSOS  True if second-order-section.
%   THISISSOS(Hd) returns 1 if filter Hd is second-order or less, and 0
%   otherwise. 
%
%   See also DFILT.   
  
%   Author: R. Losada
%   Copyright 1988-2002 The MathWorks, Inc.

% Always true 
f = true;