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

Table 4 Websites of specialist organisations and sources for grey literature

Organization	Website
Agriculture Victoria	agriculture.vic.gov.au
AHDB Horticulture	horticulture.ahdb.org.uk
Bayer	https://www.bayer.com/en/google-search.aspx
Bielefeld Academic Search Engine	https://www.base-search.net
Cost Action 1204: Food and Agriculture	https://www.vegetablegrafting.unitus.it/index.php
DuPont	https://www.dupont.co.uk
EIP-AGRI Agriculture & Innovation	ec.europa.eu/eip/agriculture
Global Agricultural Research Partnership	https://www.cgiar.org; cgspace.cgiar.org
Open Grey	https://www.opengrey.eu
EU FP7 ROOTOPOWER	https://www.rootopower.eu
H2020 TRADITOM	traditom.eu
H2020 TomGEM	tomgem.eu
H2020 TomRes	https://www.tomres.eu
Syngenta	https://www.syngenta.co.uk
Vegetable Grafting	https://www.vegetablegrafting.org
World processing tomato council	https://www.wptc.to
World Wide Science	worldwidescience.org

ISSN: 2047-2382