Possible homologies between photorefractoriness in sheep and birds : the effect of thyroidectomy on the length of the ewe's breeding season T. J. NICHOLLS, B. K. FOLLETT, A. R. GOLDSMITH and H. PEARSONReprod. Nutr. Dévelop., 28 2B (1988) 375-386DOI: https://doi.org/10.1051/rnd:19880304