Hartup, W. W. (1996). Friendships and adaptation in the life course. Psychological Bulletin, 119(3), 727-753.
Assuming that you are referring to a general topic of children playing in a sandbox, I will provide a comprehensive paper on the benefits of sandbox play for children. two+kids+one+sandbox+original+video+full+exclusive
Taylor, M. (2013). The importance of play for children's mental health. Journal of Mental Health, 22(2), 131-139. Hartup, W
Sandbox play has been a staple of childhood for generations. It provides a unique environment for children to engage in open-ended play, where they can experiment, explore, and learn through hands-on experiences. The sandbox is a place where children can express themselves freely, without the constraints of structured activities or adult-directed play. Friendships and adaptation in the life course
Gordon, T. (2001). The impact of play on children's emotional development. Journal of Applied Developmental Psychology, 22(5), 561-573.