History 95 Mental illness 69 History and criticism 58 Literature 47 Statistics 41 Philosophy 36 Mathematics 33 Biography 30 Social sciences 30 Management 29 Mass media 29 Economics 28 Education 27 Criticism and interpretation 26 English literature 26 Research 26 Sociology 26 Psychology 25 Women 25 Natural enemies 24 Taxonomy and Evolution 22 Mental Illness 21 Pathogens, Parasites and Infectious Diseases (Wild Animals), (New March 2000) 21 Plant Pests, (New March 2000) 21 Criticism 20 Fiction 20 Plants 20 Social aspects 20 Biological Control 19 Biological control 18