1. Banga, O. and L.Smeets, 1956. Some effects of the photoperiod on growth and pithiness of radish. Euphytica 5: 196–204.
2. Garner, W. W. and H. A.Allard, 1920. Effect of the relative length of day and night and other factors of the environment on growth and reproduction in plants. Journ. of Agr. Res. 18: 553–606.
3. Johansson, N., 1927. Einige Versuche über die Einwirkung verschiedener Belichtung auf die vegetative Entwicklung von Raphanus sativus L. Flora 121: 222–235.
4. Los, G. J., 1962. (Institute of Horticultural Engineering, Wageningen). Personal communications.
5. Meijer, G., 1962. (Philips Incandescent Lamp Works, Eindhoven). Personal communications.