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Colwyn M. Thomas, David A. Jones, Martin Parniske, Kate Harrison, Peter J. Balint-Kurti, Kostas Hatzixanthis, Jonathan D. G. Jones, Characterization of the Tomato Cf-4 Gene for Resistance to Cladosporium fulvum Identifies Sequences That Determine Recognitional Specificity in Cf-4 and Cf-9, The Plant Cell, Vol. 9, No. 12 (Dec., 1997), pp. 2209-2224
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Thomas et al. (1997) studied this question.
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