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A. R. Hardy, R. J. Quy, L. W. Huson, Estimation of Age in the Norway Rat (Rattus norvegicus Berkenhout) from the Weight of the Eyelens, Journal of Applied Ecology, Vol. 20, No. 1 (Apr., 1983), pp. 97-102
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Hardy et al. (1983) studied this question.
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