OGRAJŠEK, Simon, et al. “The Impact of the Period of Sowing and Fertilization on Morphological Characteristics and Seed Yield of Garden Poppy (Papaver Somniferum L.)”. Acta Agriculturae Slovenica, vol. 107, no. 1, Apr. 2016, pp. 219–228, https://doi.org/10.14720/aas.2016.107.1.20.