Superconductivity in two-leg spin ladders L. Leonyuk, G.-J. Babonas, R. Szymczak, H. Szymczak, M. Baran A. Rėza, V. Maltsev, L. Shvanskaya and V. RybakovEurophys. Lett., 45 3 (1999) 387-392DOI: https://doi.org/10.1209/epl/i1999-00176-1