@misc{indiciae7ea83209ee7f,
  title = {Variables determining concept conservation in children.},
  author = {I E Sigel and E Saltz and W Roskind},
  year = {1967},
  doi = {10.1037/h0021278},
  url = {https://pubmed.ncbi.nlm.nih.gov/6065465/},
  note = {Source identifier: 6065465}
}