@misc{indiciae32560ed5e1ce,
  title = {Physical activity, motor development and self-concept: race and age differences.},
  author = {T J Martinek and J T Cheffers and L D Zaichkowsky},
  year = {1978},
  doi = {10.2466/pms.1978.46.1.147},
  url = {https://pubmed.ncbi.nlm.nih.gov/643470/},
  note = {Source identifier: 643470}
}