K. Uhlendorf, G. Notni, and R. Kowarschik, "Reflection-type double-pass confocal microscopy with a phase-conjugate mirror,"
in Advances in Photorefractive Materials, Effects and Devices, P. Andersen, P. Johansen, H. Pedersen, P. Petersen, and M. Saffman, eds.,
Vol. 27 of Trends in Optics and Photonics
(Optical Society of America, 1999), paper AD15.