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2. Anonymous, 1850. Couve tronchuda or Portugal Cabbage. The Gardeners' Chronicle. p. 630.
3. Anonymous, 1896. Guia de Horticultura Pratica. Casa Frederico Daupias. Lisboa. 156 pp.
4. Bailey, L.H., 1922. The cultivated Brassicas I. Gentes Herbarum 1(2):51–108.
5. Bailey, L.H., 1930. The cultivated Brassicas II. Gentes Herbarum 2(5):211–267.