Guram Bezhanishvili Mai Gehrke Ray Mines Patrick J. Morandi Profinite Completions and Canonical Extensions of Heyting Algebras. 143-161 2006 23 Order 2-3 http://dx.doi.org/10.1007/s11083-006-9037-x db/journals/order/order23.html#BezhanishviliGMM06