Bulgarian dialects are the regional varieties of the Bulgarian language, a South Slavic language. Bulgarian dialectology dates to the 1830s and the pioneering work of Neofit Rilski, Bolgarska gramatika. Other notable researchers in this field include Marin Drinov, Konstantin Josef Jireček, Lyubomir Miletich, Aleksandar Teodorov-Balan, Stoyko Stoykov.