1. Dislocations in wave trains
2. M. Berry, Singularities in waves and rays, in Physics of Defects, R. Balian, M. Kleman, J.-P. Poirier (Eds.), pp. 453–549, North-Holland, Amsterdam, 1981.
3. Optical Vortices and Their Propagation
4. M. Soskin, M. Vasnetsov, Photonic Science News 4 (1999) 21. This accessible, up to date review contains a very complete, highly useful list of references.
5. M. Vasnetsov, K. Staliunas, Optical Vortices, Nova Science Publ., N.Y. Commack, 1999.