1. Aarts, H.F.M., E.E. Biewinga, G. Bruin, and H. Edel Band Korevoar. 1988.Milkveehouderij en milieu, Report No. 111. Lelystad, The Netherlands: Proofstation voor de Rundveehouderij.
2. Andersen, H.E. and K.L. Ingvartsen. 1991.Performance of Fattening Bulls Dependent on Housing System and Stocking Density. Rep. 686. Foulum, Denmark: Natl. Inst. Anim. Sci. 31 pp. [With English Summary.]
3. Arave, C.W. 1975. Behaviour, milk yield and leucocytes of dairy cows in reduced space and isolation.Journal of Dairy science 57: 1497–1501.
4. Bawden, R.J. 1991. Systems thinking and practice in agriculture.Journal of Dairy Science 74: 2362–2373.
5. Blaxter, K.L. 1962.The Energy Metabolism of Ruminants. London, U.K.: Hutchinson and Co. p. 196.