Agriculture 77 Turismo 27 Tourism 26 Travel and state 25 Agricultura 20 Research 18 Soil science 10 History 9 Agricultural engineering 8 Historia 8 Agricultural ecology 6 Ciencias sociales 6 Soils 6 Breeding 5 Rural development 5 Sustainable agriculture 5 AGRICULTURA 4 Agronomy 4 Biology 4 Black studies 4 Estudios de los negros 4 General 4 PUBLICACIONES PERIODICAS 4 Pe ́dologie 4 Social science 4 Sols 4 Zeitschrift 4 Agricultural administration 3 Agricultural innovations 3 Arid regions agriculture 3