Lionel Robbins (1932, 1935, 2nd ed.). An Essay on the Nature and Significance of Economic Science, London: Macmillan. Links for 1932 HTML and 1935 facsimile.
Amartya Sen (2008). "Social Choice,". The New Palgrave Dictionary of Economics, 2nd Edition, Abstract & TOC.
scribd.com
Lionel Robbins (1932, 1935, 2nd ed.). An Essay on the Nature and Significance of Economic Science, London: Macmillan. Links for 1932 HTML and 1935 facsimile.
yale.edu
cowles.econ.yale.edu
For example, in Kenneth J. Arrow (1951). Social Choice and Individual Values, New York: Wiley, ch. II, section 2, A Notation for Preferences and Choice, and ch. III, "The Social Welfare Function".