Papalia, D.; Fitzgerald, J.; Hooper, F. H. (1971). “Piagetian Theory and the Aging Process: Extensions and Speculations”. 《The International Journal of Aging and Human Development》 2: 3–20. doi:10.2190/AG.2.1.b. S2CID143590129.
Papalia, D.; Fitzgerald, J.; Hooper, F. H. (1971). “Piagetian Theory and the Aging Process: Extensions and Speculations”. 《The International Journal of Aging and Human Development》 2: 3–20. doi:10.2190/AG.2.1.b. S2CID143590129.