Witter, Sidia, and Betina Blochtein. “Effect of Pollination by Bees and Other Insects on the Production of Onion Seeds”. Pesquisa Agropecuaria Brasileira, vol. 38, no. 12, Dec. 2003, pp. 1399-07, doi:10.1590/S1678-3921.pab2003.v38.6717.