White, AG; Smith, CP; Heckenberg, NR; Rubinsztein-Dunlop, H; McDuff, R; Weiss, CO; Tamm, C (1991). "Interferometric measurements of phase singularities in the output of a visible laser". Journal of Modern Optics. 38 (12): 2531–2541. Bibcode:1991JMOp...38.2531W. doi:10.1080/09500349114552651.
White, AG; Smith, CP; Heckenberg, NR; Rubinsztein-Dunlop, H; McDuff, R; Weiss, CO; Tamm, C (1991). "Interferometric measurements of phase singularities in the output of a visible laser". Journal of Modern Optics. 38 (12): 2531–2541. Bibcode:1991JMOp...38.2531W. doi:10.1080/09500349114552651.