1. Benlloch, S., Pottschmidt, K., Wilms, J. et al. 2004, AIPC, 714, 61.
2. Bowyer, S., Byram, E. T., Chubb, T. A. et al. 1965, Science, 147, 394.
3. Dong Ai-Jun, 2012, Astronomical Research & Technology, 9(3), 1672.
4. Jurkevich, I. 1971, AP&SS, 13, 154.
5. Kidger, M., Takalo, L., Sillanpaa, A. 1992, A&A, 264, 32.