1. C.J.R. Sheppard, The use of lenses with an annular aperture in scanning optical microscopy. Optik 48, 329–334 (1977)
2. C.J.R. Sheppard, A. Choudhury, Image formation in the scanning microscope. J. Mod. Opt. 24, 1051–1073 (1977)
3. C.J.R. Sheppard, T. Wilson, Depth of field in the scanning microscope. Opt. Lett. 3, 115–117 (1978)
4. C.J.R. Sheppard, T. Wilson, Imaging properties of annular lenses. Appl. Opt. 18, 3764–3769 (1979)
5. C.J.R. Sheppard, T. Wilson, Fourier imaging of phase information in conventional and scanning microscopes. Phil. Trans. Roy. Soc. A295, 513–536 (1980)