 Gleason founded the theory of Dirichlet algebras , and made other math ­ e ­ mat ­ i ­ cal contributions including work on the enumerative combinatorics of permutations . ( In 1959 he wrote that his research " sidelines " included " an intense interest in combinatorial problems . " ) As well , he was not above publishing research in more elementary mathematics , such as the derivation of the set of polygons that can be constructed with compass , straightedge , and an angle trisector . 
