According to Augustine Brannigan's "The social basis of scientific discoveries", the classical papers on simultaneous discoveries are: 1. A.L. Kroeber(1917): "The superorganic". American Anthropologist, 19 (2), p. 163-213. 2. William Ogburn & Dorothy Thomas (1922): "Are inventions inevitable? A note on social evolution". Political Science Quarterly, 37 (1), p. 83-98. Best wishes Ramon Garcia Fernandez