Ramaswamy, Vijaya (1993). "Women and Farm Work in Tamil Folk Songs". Social Scientist (Social Scientist) 21 (9/11): 113–129. doi:10.2307/3520429. "As early as the Tolkappiyam (which has sections ranging from the 3rd century BC to the 5th century AD) the eco-types in South India have been classified into ...".
