The Sangam literature can be considered as the ancient predecessor of Malayalam.[76] Malayalam literature starts from the Old Malayalam period (9th–13th century CE) and includes such notable writers as the 14th-century Niranam poets (Madhava Panikkar, Sankara Panikkar and Rama Panikkar),[77][78] and the 16th-century poet Thunchaththu Ezhuthachan, whose works mark the dawn of both the modern Malayalam language and its poetry.[79] For the first 600 years of Malayalam calendar, the literature mainly consisted of the oral Ballads such as Vadakkan Pattukal in North Malabar and Thekkan Pattukal in Southern Travancore.[80] Designated a "Classical Language in India" in 2013,[81] it developed into the current form mainly by the influence of the poets Cherusseri Namboothiri,[82][83] Thunchaththu Ezhuthachan,[83] and Poonthanam Nambudiri,[83][84] in the 15th and the 16th centuries of Common Era.[83][85] Unnayi Variyar,[86] a probable poet of 17th/18th century CE, and Kunchan Nambiar, a poet of 18th century CE, have also influenced a lot in the growth of modern Malayalam literature in its pre-mature form.[83] The Bharathappuzha river, also known as River Ponnani, and its tributaries, have played a major role in the development of modern Malayalam Literature.[87]