CONCEPTShttp://cat.aii.caas.cn/concept/2144cat.aii.caas.cnhttp://dewey.info/class/759.1/dewey.infohttp://eurovoc.europa.eu/1615eurovoc.europa.euhttp://lod.gesis.org/thesoz/concept/10035407lod.gesis.orghttp://lod.nal.usda.gov/nalt/7527lod.nal.usda.govhttp://stitch.cs.vu.nl/vocabularies/rameau/ark:/12148/cb11930875kstitch.cs.vu.nlhttp://www.eionet.europa.eu/gemet/concept/5693www.eionet.europa.euhttp://www.fao.org/countryprofiles/geoinfo/geopolitical/resource/northern_Americawww.fao.orghttp://zbw.eu/stw/descriptor/17806-6zbw.eu。