TY - JOUR T1 - A ROTATING CROSS-CYLINDER JF - British Journal of Ophthalmology JO - Br J Ophthalmol SP - 632 LP - 633 DO - 10.1136/bjo.23.9.632 VL - 23 IS - 9 AU - M. Tree Y1 - 1939/09/01 UR - http://bjo.bmj.com/content/23/9/632.abstract N2 - 300 Multiple ChoicesThis is a pdf-only article and there is no markup to show you.full-text.pdf ER -