1. Hardwick, C. (ed.). (1977). Semiotic and Significs: The Correspondence between Charles S. Peirce and Victoria Lady Welby. Bloomington: Indiana University Press.
2. Lieb, I. C. (ed.). (1953). Charles S. Peirce’s Letters to Lady Welby. New Haven: Whitlock’s, Inc.
3. Peirce, C. S. (1958). Values in a Universe of Chance. Selected Writings. P. Wiener (Ed.). Mineola: Dover Publications.
4. Ransdell J. (1977). Some Leading Ideas of Peirce’s Semiotic, Semiotica 19, 157–178.