Grupen, C. G., McIlfatrick, S. M., Ashman, R. J., Boquest, A. C., Armstrong, D. T., & Nottle, M. B. (2003). Relationship between donor animal age, follicular fluid steroid content and oocyte developmental competence in the pig. Reproduction, Fertility and Development, 15(2), 81-87.

Grupen, Christopher G., Stephen M. McIlfatrick, Rodney J. Ashman, Andrew C. Boquest, David T. Armstrong, and Mark B. Nottle. "Relationship Between Donor Animal Age, Follicular Fluid Steroid Content and Oocyte Developmental Competence in the Pig." Reproduction, Fertility and Development 15, no. 2 (2003): 81-87.

Grupen, Christopher G., et al. "Relationship Between Donor Animal Age, Follicular Fluid Steroid Content and Oocyte Developmental Competence in the Pig." Reproduction, Fertility and Development, vol. 15, no. 2, 2003, pp. 81-87.