1. Kibble, T. W. B. J. Phys. A9, 1387–1398 (1976).
2. Zurek, W. H., Nature 317, 505–508 (1985).
3. Zurek, W. H. Acta phys. pol. B24, 1301–1311 (1993).
4. Kibble, T. W. B. Nature 317, 472 (1985).
5. Donnelly, R. J. Quantized Vortices in Helium II (Cambridge Univ. Press, 1991).