1. Noordham, D. 1973. Identification of plant viruses. Methods and Experiments. Centre for Agric. Pub. β Doc., Wageningen, the Netherlands, 207 p.
2. Shepard, J.F. 1972. Gel-diffusion methods for the serological detection of potato viruses X, S, and M. Montana Agric Exp Stn Bul 662, Bozeman, MT 72 p.