The maximal mid-expiratory flow rate (FEF 25-75 per cent).

@article{Leiner1969TheMM,
  title={The maximal mid-expiratory flow rate (FEF 25-75 per cent).},
  author={G C Leiner and Susan Abramowitz and Mitchell Small},
  journal={Review of allergy},
  year={1969},
  volume={23 5},
  pages={387-8}
}