1. Gan, Woon Siong. 2007. Gauge Invariance Approach to Acoustic Fields, Acoustical Imaging. In vol. 29, ed. I. Akiyama, 389–394. Springer.
2. Yang, C.N., and R.L. Mills. 1954. Conservation of isotopic spin and isotopic gauge invariance. Physical Review 96 (1): 191–195.
3. Ryder, L.H. 1991. Quantum Field Theory, 2nd edn. Cambridge University Press.
4. Kittel, C. 1963. Quantum Theory of Solids. New York: John Wiley.
5. Dartora, C.A., and G.G. Cabrera. 2008. The electron–phonon interaction from fundamental local gauge symmetries in solids. Phys. Rev. B 78: 012403.