Faster backtracking algorithms for the generation of symmetry-invariant permutations. Moreno, Oscar, Ramírez, John, Bollman, Dorothy, Orozco, Edusmildo (2002) Journal of Applied Mathematics
From Bi-ideals to Periodicity Jānis Buls, Aivars Lorencs (2008) RAIRO - Theoretical Informatics and Applications The necessary and sufficient conditions are extracted for periodicity of bi-ideals. They cover infinitely and finitely generated bi-ideals.