Mauricio Featherman John D. Wells The Intangibility of E-Services: Effects on Artificiality, Perceived Risk, and Adoption. 2004 HICSS http://csdl.computer.org/comp/proceedings/hicss/2004/2056/07/205670177babs.htm db/conf/hicss/hicss2004-7.html#FeathermanW04