Lewis, R. W., and J. A. Lentfer. 1967. The vitamin A content of polar bear liver: range and variability. Compar. Biochem. Physiol. 22:923-926. | Lewis, R. W., and J. A. Lentfer. 1967. The vitamin A content of polar bear liver: range and variability. Compar. Biochem. Physiol. 22:923-926. |