Markus Püschel Martin Rötteler Algebraic signal processing theory: Cooley-Tukey type algorithms on the 2-D hexagonal spatial lattice. 259-292 2008 19 Appl. Algebra Eng. Commun. Comput. 3 http://dx.doi.org/10.1007/s00200-008-0077-x db/journals/aaecc/aaecc19.html#PuschelR08