1. Trial set of small lenses and a modified trial-frame;Jackson;Trans Am Ophthalmol Soc,1885
2. The astigmic lens (crossed cylinder) to determine the amount and principal meridians of astigmia;Jackson;Ophth Rec,1907
3. The "crossed cylinder" in the determination of the refraction;Schneideman;Ophth Rec,1900
4. The crossed-cylinder tests, especially in relation to the astigmatic axis;Crisp;Am J Ophthalmol,1932
5. A plea for the more general use of the cross cylinder;Crisp;Am J Ophthalmo,1923