Andretta, V., Giampapa, M. S., Covino, E., Reiners, A., & Beeck, B. (2017). Estimates of Active Region Area Coverage through Simultaneous Measurements of the He I λλ 5876 and 10830 Lines. Astrophysical Journal, 839(2): 97. doi:10.3847/1538-4357/aa6a14.