D. Nicholls, M. Dopita, H. Jerjen, and G. Meurer. (2011)cite arxiv:1107.3898Comment: 13 figures, 3 table. Accepted for publication in The Astronomical Journal.
D. Brisbin, and M. Harwit. (2011)cite arxiv:1110.5862
Comment: 27 pages plus bibliography 4 figures 3 supplementary online figures
ascii data tables available.
D. Makarov, and R. Uklein. (2012)cite arxiv:1204.5406Comment: 17 pages, 6 figures, 2 tables, to be published in Astrophysical Bulletin 67, p.123 (2012).