1. 1. Chavasse FB: in Worth's Squint. London Bailliere Tindall & Cox 1939. pp 172-176.
2. 2. Hamburger FA: Stellungsanomalien in Velhagen K: Der Augenarzt. Stuttgart. G Thieme. 1960. vol 3. p 88.
3. 3. von Noorden GK: Burian-von Noorden's Binocular Vision and Ocular Motility: Theory and Management of Strabismus ed 2. St Louis CV Moshy 1980.
4. 4. Duke-Elder S Wybar K: Ocular Motility and Strabismus. System of Ophthalmology. St Louis CV Moshy 1973 vol 6 p 238.
5. 5. Parks MM: Ocular Motility and Strabismus. Hagerstown. Harper & Row 1975 p 109.