Participant observation 14 History 10 Research 10 Agricultural Extension 7 Methodology 6 Mass media 5 Action research 4 Medicine 4 Social sciences 4 Agricultural extension 3 Clinical Trials as Topic 3 Clinical trials 3 Education 3 Ethnologie 3 Feldforschung 3 Historians 3 Journalism 3 Methodologie 3 Politics and government 3 Research Design 3 Sensory evaluation 3 Social aspects 3 Social conditions 3 Sociology 3 Visual anthropology 3 Active learning 2 Adolescent 2 Child 2 Children's rights 2 Comparative government 2