1. Anonymous. 1991. Importation of potatoes from Canada-Rules and Regulations, Animal and Plant Health Inspection Service. US Dept Agric Federal Register Vol 58, No 83, April 30, 1991, pp. 19789–19791.
2. Bagnall, R.H., R.H. Larson and J.C. Walker. 1956. Three virus components of “interveinal mosaic” -Irish Cobbler potato. Am Potato J 33: 271–273.
3. Bawden, F.C. and B. Kassanis. 1951. Serologically-related strains of potato virus Ythat are not mutually antagonistic in plants. Ann Appl Biol 38: 402–410.
4. Bercks, R. 1970. Potato virus X. No. 4.In: Descriptions of plant viruses. Commonw Mycol Inst/Assoc Appl Biol, Kew, England.
5. Brücher, H. 1969. Observations on the origin and expansion of YN-virus in South America. Angewandte Botanik 43: 241–249. (in German).