1. S. Ferrara, R. Kallosh and A. Strominger, N=2 Extremal Black Holes, Phys. Rev. D52, 5412 (1995), hep-th/9508072.
2. A. Strominger, Macroscopic Entropy of N=2 Extremal Black Holes, Phys. Lett. B383, 39 (1996), hep-th/9602111.
3. S. Ferrara and R. Kallosh, Supersymmetry and Attractors, Phys. Rev. D54, 1514 (1996), hep-th/9602136.
4. S. Ferrara and R. Kallosh, Universality of Supersymmetric Attractors, Phys. Rev. D54, 1525 (1996), hep-th/9603090.
5. S. Ferrara, G. W. Gibbons and R. Kallosh, Black Holes and Critical Points in Moduli Space, Nucl. Phys. B500, 75 (1997), hep-th/9702103.