Social groups: religious groups and communities 14 History of the Americas 13 Gender studies, gender groups 12 European history 10 Social and cultural history 10 Library & information services 8 Literature: history and criticism 8 Literature: history & criticism 6 Biography: general 4 Judaism 4 Teaching skills & techniques 4 problem-based learning 4 Aircraft and aviation 3 Biography: historical, political and military 3 Europe 3 General and world history 3 Organization & management of education 3 Regional studies 3 Second World War 3 Social & cultural history 3 The Holocaust 3 Veterinary medicine 3 c 1940 to c 1949 3 Academic & specialist libraries 2 Acquisitions & collection development 2 Communication studies 2 Conservation of the environment 2 Data analysis: general 2 Educational strategies & policy 2 Entrepreneurship 2