L. Stoyanov, N. Gorunski, M. Mincheva, P. Drenkov, E. Lazarov, and A. Dreischuh, “Experimental Verification of the Gouy Phase for Higher-Order Hermite-Gaussian Beams”, C. R. Acad. Bulg. Sci., vol. 77, no. 8, pp. 1138–1145, Aug. 2024.