1. [At] M. F. Atiyah, “Global aspects of the theory of elliptic differential operators” in Proc. Internat. Congr. Math. (Moscow, 1966), Izdat. “Mir,” Moscow, 1968, 57–64.
2. [AS1] M. F. Atiyah and I. Singer, The index of elliptic operators, I, Ann. of Math. (2) 87 (1968), 484–530.
3. [AS2] M. F. Atiyah and I. Singer, The index of elliptic operators, III, Ann. of Math. (2) 87 (1968), 546–604.
4. [BGV] N. Berline, E. Getzler, and M. Vergne, Heat Kernels and Dirac Operators, Grundlehren Math. Wiss. 298, Springer, Berlin, 1992.
5. [Bl] B. Blackadar, $K$-Theory for Operator Algebras, 2nd ed., Math. Sci. Res. Inst. Publ. 5, Cambridge Univ. Press, Cambridge, 1998.