maximal abelian subgroups of the finite symmetric group

Let g be a group. for an element a ∈ g, denote by c^ 2 (a) the second centralizer of a in g, which is the set of all elements b ∈ g such that bx = xb for every x ∈ g that commutes with a. let m be any maximal abelian subgroup of g. then c^ 2 (a) ⊆ m for every a ∈ m. the abelian rank (a-rank) of m is the minimum cardinality of a set a ⊆ m such that ∪ a∈a c^ 2 (a) generates m. denote by sn the symmetric group of permutations on the set x = {1, . . . , n}. the aim of this paper is to determine the maximal abelian subgroups of sn of a-rank 1 and describe a class of maximal abelian subgroups of sn of a-rank at most 2.