Travers, Jeffrey; Milgram, Stanley (December 1969). "An Experimental Study of the Small World Problem". Sociometry. 32 (4): 425–443. doi:10.2307/2786545. JSTOR2786545.
Travers, Jeffrey; Milgram, Stanley (December 1969). "An Experimental Study of the Small World Problem". Sociometry. 32 (4): 425–443. doi:10.2307/2786545. JSTOR2786545.