1. Aves O.
Improvements in and relating to multifocal lenses and the like and the method of grinding same. GB Patent 15,735, 1908.
2. Orford H.
Manufacture of Lenses for Spectacles or Eyeglasses. US Patent 943,449, 1909.
3. FOUR STEPS THAT LED TO VARILUX*
4. Cretin‐maitenaz B.
Multifocal lens having a locally variable power. US Patent 2,869,422, 1959.