1. Ben-Ze'ev, N. and Zohari, D. 1973 Species relationships in the genus Pisum L. Israel J. Bot.22, 17–24.
2. Frankel, O. H. and Bennett, E. 1970 Genetic resources in plants-their exploration and conservation. Blackwell Scientific Publications, Oxford and Edinburgh.
3. Lamprecht, H. 1974 Monographie der Gattung Pisum. Steiermärkische Landesdruckerei, Graz.
4. Leppik, E. E. 1970 Gene centres of plants as sources of disease resistance. Annu. Rev. Phytopathol.8, 324–344.
5. Lie, T. A. 1971 Temperature-sensitive root-nodule formation in pea cv. Iran. Plant and Soil34, 751–752.