Arya, S C Development of scientific concepts among children: Based on piagetian tasks - Agra: National Psychological Corporation, 1993 - 159p. - Bhargava research monograph series no. 35 . ISBN: 81-85316-38-4 Subjects--Topical Terms: Scientific concepts Subjects--Index Terms: Conservation of mass Universal Decimal Class. No.: 159.922.72:165.191 / N3