1. Afanasiev, M. 1944. A study of dormancy and germination of seeds ofCercis canadensis. J. Agric. Res. 69: 405–420.
2. Aitken, Y. 1939. The problem of hard seeds in subterranean clover. Proc. Roy. Soc. Victoria 51(N.S.): 187–212.
3. Baciu-Miclaus, D. 1970. Contribution to the study of hard seed and coat structure properties of soybean. Proc. Int. Seed Testing Assoc. 35: 599–617.
4. Ballard, L. A. T. 1973. Physical barriers to germination. Seed Sci. & Technol. 1: 285–303.
5. Ballard, L. A. T. 1976. Strophiolar water conduction in seeds ofTrifolieae induced by action on the testa and non-strophiolar sites. Austral. J. Pl. Physiol. 3: 465–469.