1. Environment and animal health in piglet production: a field study of incidences and correlations;Bäckström;Dissertation, Stockholm. Acta Vet. Scand.,1973
2. Report of the technical committee to enquire into the welfare of livestock kept under intensive husbandry conditions;Brambell,1965
3. Enkele gedragskenmerken met betrekking tot het inzetten van zeugen in groepshuisvesting;Buré,1987
4. An analysis of stereotyped behaviour in tethered sows;Cronin;Ann. Rech. Vét.,1984
5. Uitvoering onderzoek in Denemarken;De Jong;Varkens,1987