1. Agrawal, J. Ultrastruct. Res. 17: 84, 1967.
2. Bock, Ann. appl. Biol. 57: 131, 1966.
3. Cadman, Virology 11: 653, 1960.
4. Cadman, Dias & Harrison, Nature, Lond. 187: 577, 1960.
5. Fritzsche & Schmidt, Naturwissenschaften 50: 163, 1963.
6. Gerola, Bassi & Betto, Caryologia 18: 353, 1965.
7. Harrison, Ann. appl. Biol. 46: 221, 1958.
8. Harrison & Cadman, Nature, Lond. 184: 1624, 1959.
9. Harrison & Nixon, Virology 12: 104, 1960.
10. Harrison & Winslow, Ann. appl. Biol. 49: 621, 1961.
11. Hollings, J. hort. Sci. 38: 138, 1963.
12. Jha, J. hort. Sci. 36: 219, 1961.
13. Jha & Posnette, Nature, Lond. 184: 962, 1959.
14. Jha & Posnette, Virology 13: 119, 1961.
15. Lister & Murant, Ann. appl. Biol. 59: 49, 1967.
16. Murant & Lister, Ann. appl. Biol. 59: 63, 1967.
17. Schmelzer, Phytopath. Z. 46: 105, 1962.
18. Schmelzer, Phytopath. Z. 46: 315, 1963.
19. Smith & Markham, Phytopathology 34: 324, 1944.
20. Taylor & Robertson, Rep. Scott. hort. Res. Inst., 1969: 63, 1970.