1. The relation of age at first calving to butterfat production in the first five lactations;Chapman,1936
2. The energy basis of measuring yield in dairy cattle;Gaines;Illinois Agr. Exp. Sta. Bull.,1928
3. The effect of age at first calving on growth, yield and economy of production;Hansson;Anim. Breed. Abstr.,1941
4. Johansson, I., and A. Hansson. 1940. Causes of variation in milk and butterfat yield of dairy cows. K. Lantbruksakad. Tidskr. Nr. 6½:1.
5. Influence of length of dry period upon the quantity of milk produced in the subsequent lactation;Klein;J. Dairy Sci.,1943