classification of maximal subrings of certain commutative rings

In this article we classify maximal subrings of certain commutative rings. for instance we classify certain maximal subrings of polynomial rings. we also classify all maximal subrings of finite direct product of rings and consequently we classify all of the maximal subrings of product of two fields. finally we classify maximal subrings of k[x]/(x^2), where kis a field.