P. Konsin, N. Kristoffel, and P. Rubin, The behavior of superconducting gaps in a two-band model of HTSC, Low Temp. Phys. 22, 405–407, (1996) [Fiz. Nizk. Temp. 22, 527-530, (1996)] DOI: https://doi.org/10.1063/10.0034001.