1. Boyer, C. B., & Merzbach, U. C. (2011). A history of mathematics. London: John Wiley & Sons.
2. Breckenridge, W., & Magidor, O. (2012). Arbitrary reference. Philosophical Studies, 158(3), 377–400.
3. Fine, K. (1985). Reasoning with arbitrary objects. OUP Press.
4. Frege, G. (1891). Function and concept. In P. Geach & M. Black (Eds.), Translations from the philosophical writings of Gottlob Frege (pp. 137–156). Oxford: Blackwell.
5. Frege, G. (1904). What is a function? In B. MacGuinness (Ed.), Collected Papers in Mathematics, Logic and Philosophy (pp. 285–292). Oxford: Blackwell.