[6] Porras M A. Finiteness and propagation law of the power density second-order moment for diffracted scalar light beam [J]. Optik, 1999, 110(9): 417-420.

[7] Porras M A. Non-paraxial vectorial moment theory of light beam propagation [J]. Opt. Commun., 1996, 127(6): 79-95.

[8] Kang Xiaoping, Lü Baida. Vectorial nonparaxial flattened Gaussian beams and their beam quality in terms of the power in the bucket [J]. Opt. Commun., 2006, 262(1): 1-7.

[9] Siegman A E. New developments in laser resonators [C]. Proc. of SPIE, 1990, 1224: 2-14.