@misc{indiciae21ddd55037ae,
  title = {DIFFICULTY FACTORS AND NON-LINEAR FACTOR ANALYSIS.},
  author = {R P MCDONALD},
  year = {1965},
  doi = {10.1111/j.2044-8317.1965.tb00690.x},
  url = {https://pubmed.ncbi.nlm.nih.gov/14324840/},
  note = {Source identifier: 14324840}
}