  Tarski 1986 is a brief and cogent exposition of the permutation-invariance approach. For elaboration and criticism, see McCarthy 1981, van Bentham 1989, Sher 1991, McGee 1996, Feferman 1999 and 2010, Bonnay 2008, and Dutilh Novaes 2014. Bonnay 2014 surveys recent work in this area. 