Arora, Rita, and Poonam. “A Comparative Study of Multi-Grade Teaching on the Achievement Levels in Hindi and Mathematics of Second Standard in Government and NGO Schools”. INDIAN EDUCATIONAL REVIEW, vol. 51, no. 2, July 2013, pp. p. 82-93, http://14.139.250.109:8090/index.php/ier/article/view/2786.