Terrorism 53 Terrorists 21 September 11 Terrorist Attacks, 2001 13 Prevention 8 Muslims 7 History 6 Social aspects 6 Social conditions 6 Emergency management 5 Islam 5 Politics and government 5 Psychological aspects 5 Jihad 4 Journalism 4 LAW / Comparative 4 Law and legislation 4 National security 4 Peace 4 War on Terrorism, 2001-2009 4 Globalization 3 Government policy 3 Intelligence service 3 International relations 3 Internet 3 Islam and politics 3 Islamic fundamentalism 3 Popular culture 3 Religious aspects 3 Social Sciences 3 Sociology and anthropology 3