http://www.useit.com/alertbox/20030120.html http://www.amazon.com/exec/obidos/ISBN%3D155860569X/useitcomusableinA/ http://www.amazon.com/exec/obidos/ISBN=0262621088/useitcomusablein/ http://www.nngroup.com/reports/roi/ http://www.nngroup.com/reports/tips/usertest/ http://www.nngroup.com/reports/tips/recruiting/ http://www.nngroup.com/services/workshops/learnbydoing.html http://www.nngroup.com/events/tutorials/intro_user_testing.html http://www.nngroup.com/events/ http://www.useit.com/alertbox/