 Other important 19th-century developments included the fabulist Ivan Krylov; non-fiction writers such as the critic Vissarion Belinsky and the political reformer Alexander Herzen; playwrights such as Aleksandr Griboyedov, Aleksandr Ostrovsky and the satirist Kozma Prutkov (a collective pen name).The beginning of the 20th century ranks as the Silver Age of Russian poetry.Well-known poets of the period include