1. A comparison, under different degrees of brightness, of minimum visual distances of two luminous points and of a broken circle;Berger;Amer. J. Psychol.,1942
2. Conrady , A. E. 1913 Footnote to Lister (1913)
3. Ein Vorschlag zur Vereinfachung der Sehproblem;Guillery;Arch. f. Augenheilk.,1891