N-Sum-Groups is a project mainly written in ..., it's free.
A mathematics article detailing Cohn's results of when a group can be written as a product of proper subgroups.
n-Sum Groups
ABSTRACT: "We analyze when a group can be written as the prod- uct of its proper subgroups. We follow the work of Cohn by proving the necessary machinery in detail and then proving some of the main theorems, including the necessary and sufficient conditions for writing groups as a product of 2 through 4 subgroups. This paper was written as part of a class project."