 Due to the predominantly oral character of Serbian epic poetry, the names of the original authors of many epic poems have been lost over time.The varying and meandrous style of the "guslari", whereby the text of a published poem would not match word for word with that sung during a live performance, is due to the nature of epic poetry recitation itself.According to Slavic studies professor David A. Norris, the "guslar" "did not know his songs by heart, but as compositions made up of traditional phrases and formulaic expressions on which he could call each time he sang.