1. Backus, G.B., Bokma, I.S., Gommers, T.A., De Koning, R., 1991. Farm systems with cubicles, tethered sows and group-housing. In: Report P1.61. p1. Res.Inst. Pig Husbandry, Rosmalen, The Netherlands.
2. Backus, G.B., Vermeer, H.M., Roefols, P.C., Vesseur, P.C., Adams, J.H.A.N., van der Wilt, F.J., 1997. Comparison of four housing systems for non-lactating sows. In: Report P1.61. p1. Res. Inst. Pig Husbandry, Rosmalen, The Netherlands.
3. Effects of pen size, partial stalls and method of feeding on welfare-related behavioral and physiological responses of group-housed pigs;Barnett;Appl. Anim. Behav. Sci,1992
4. Environmental and animal health in piglet production;Bäckström;Acta Vet. Scand. Suppl,1973
5. Broom, D.M., Potter, M.J., 1984. Factors affecting the occurrence of stereotypies in stall-housed dry sows. In: J. Unshelm, G. van Putten K. Zeeb Eds., Proceedings of the International Congress on Applied Ethology in Farm Animals. Darmstadt, Germany, KTLB, pp. 229–231.