1. A microscope focusing technique for a digital image analysing system;Dähne;Optik,1980
2. Simple focusing criterion;Häusler;Applied Optics,1984
3. The frequency response of a defocused optical system;Hopkins,1955
4. Microcomputer controlled automatic image focusing system;Kalpagam,1986
5. Symmetries in coherent and partially coherent fields;Lohmann;Optica acta,1983