Famous dataset of the terrorists involved in the 9/11 bombing of the World Trade Centres in 2011. Data was extracted from news reports and ties range from ‘at school with’ to ‘on same plane’. 1-mode matrix 19 x 19 person by person of trusted prior contacts and 1-mode matrix 61 x 61 of other associates. Ties are undirected and binary. Relations are a mix of prior-contacts like trained together, lived together, financial transactions, at school with, on same flight.