MOESM4 of What evidence exists on the effectiveness of the techniques and management approaches used to improve the productivity of field grown tomatoes under conditions of water-, nitrogen- and/or phosphorus-deficit? A systematic map protocol

Additional file 4. Comparison and selection of Subject Categories for bibliographical databases. Lists and comparison of the subject categories or research areas by which subjects are categorised in the different bibliographical database sources consulted. Comparison between the subject categories from the different database sources allowed to identify common and equivalent categorisation for the selection of relevant subjects in the literature search.