The concept of the Invisible Foot initially appears in 1973 in the JEI.  The article by E.K. Hunt and d' Arge is entitled "On Lemmings and Other Acquisitive Animals: Propositions on Consumption."  In later articles Hunt again discusses the Invisible Foot and then references this article.  One particularly powerful rendition of this concept appears in Hunt's 1981 paper "A Radical Critique of Welfare Economics."  This article appears in E.J. Nell (ed.) Growth, Profits and Property.  Both articles are a must read as far as I am concerned, particularly if you are interested in radical critiques of traditional neoclassical welfare economics concepts.
 
Justin A. Elardo