Ono (1914) conjectured that the inequality
 |
holds true for all triangles, where 
, 
,
and 
are the lengths of the sides and 
is the area of the triangle.
This conjecture was shown to be false by Quijano (1915), although it was subsequently
proved to be true for acute triangles by Balitrand
(1916). A simple counterexample is provided by the triangle with 
, 
, and 
.
