1. K. Astala, T. Iwaniec, G. Martin, Elliptic Partial Differential Equations and Quasiconformal Mappings in the Plane (Princeton University Press, Princeton, 2009)
2. M.F. Atiyah, I.M. Singer, The index of elliptic operators on compact manifolds. Bull. Am. Math. Soc. 69(3), 422–433 (1963)
3. M. Atiyah, D. Iagolnitzer (eds.), Fields Medalists Lectures (World Scientific, Singapore, 1997)
4. B. Bojarski, On a boundary problem for a system of elliptic first-order partial differential equations. Dokl. Akad. Nauk SSSR 102, 201–204 (1955) [in Russian]
5. B. Bojarski, Homeomorphic solutions of Beltrami systems. Dokl. Akad. Nauk SSSR 102, 661–664 (1955) [in Russian]