Building on work of Huntington (1933ab), Robbins conjectured that the equations for a Robbins algebra, commutativity, associativity, and the Robbins
axiom

where
denotes NOT and denotes OR, imply those for a Boolean algebra. The conjecture was finally proven
using a computer (McCune 1997).

Fitelson, B. "Using Mathematica to Understand
the Computer Proof of the Robbins Conjecture." Mathematica in Educ. Res.7,
17-26, 1998. http://library.wolfram.com/infocenter/Articles/1475/. Fitelson, B. "Proof of the Robbins Conjecture." http://library.wolfram.com/infocenter/MathSource/291/.Huntington,
E. V. "New Sets of Independent Postulates for the Algebra of Logic, with
Special Reference to Whitehead and Russell's Principia Mathematica."
Trans. Amer. Math. Soc.35, 274-304, 1933a.Huntington,
E. V. "Boolean Algebra. A Correction." Trans. Amer. Math. Soc.35,
557-558, 1933b.Kolata, G. "Computer Math Proof Shows Reasoning
Power." New York Times, Dec. 10, 1996.McCune, W. "Solution
of the Robbins Problem." J. Automat. Reason.19, 263-276, 1997.McCune,
W. "Robbins Algebras are Boolean." http://www.cs.unm.edu/~mccune/papers/robbins/.Nelson,
E. "Automated Reasoning." http://www.math.princeton.edu/~nelson/ar.html.