1. British Standards Institution BS EN ISO 13666: 2019 (TC): Ophthalmic optics – Spectacle lenses – Vocabulary. London: BSI; 2019.
2. British Standards Institution (1998) BS EN ISO 7944:1998: Optics and optical instruments-Reference wavelengths. London: BSI; 1998.
3. British Standards Institution BS 7394-2: 2007 Complete spectacles part 2: Specification for prescription spectacles. London BSI; 2007
4. Brooks C and Borish I (2007) System for Ophthalmic Dispensing 3rd edn. America: Butterworth Heinemann p. 407
5. Wilson D and Daras S (2014) Practical Optical Dispensing 3rd edn. Australia: The Open Training and Education Network. p.66