1. Bailey, L. H. 1949. Manual of cultivated plants. Rev. ed. 1116 p.
2. Bouquet, A. G. B. 1950. Sprouting broccoli. Oregon Agr. Exp. Sta., Bull. 704. 7 p.
3. de Candolle, Alphonse. 1885. Origin of cultivated plants. 468 p.
4. Cato, Marcus Porcius. 1934. On agriculture. [Translated by William Davis Hooper. Revised by Harrison Boyd]. 542 p.
5. Engler, A. 1919. Das Pflanzenreich. 4 (105, Pars 1): 32.