How do you encode "a < b = c" in content MathML?

Perhaps you'll tell me to read the manual, but I wondered: How do you encode
   A = b = c
   a < b < c
   a < b = c
etc in content MathML?

In fact, I had a look at the manual and the closest I could find is
    http://www.w3.org/TR/2009/WD-MathML3-20090924/chapter4.html#contm.nary.reln



Jonathan


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